PDA

View Full Version : Piston/barrel dramas



jellywrestler
31st August 2011, 09:20
just pulled a barrel off and found some lovely marks in it, these are both sides of the barrel and there's similar marks at the bottom.
From the top the piston looks all good but has started to go bad on the sides particularly above the gudgeon pin area, rings are had it.
285 miles on a new sleeve and piston it's a twin cylinder two carbs what went wrong?

F5 Dave
31st August 2011, 17:14
Bleeding heck Spyda, that's queer. But how thin is that sleeve? Is there something queer about the gungeon pin-small end arrangement? Or clearance of the piston inner to the rod? Can't quite see the circlip arrangement:confused:

pete376403
31st August 2011, 23:56
gudgeon pin circlip come out?
I preferred teflon buttons over pin clips for this very reason in my speedway bike motors.

gammaguy
1st September 2011, 02:15
what sort of engine is this?

Grumph
1st September 2011, 05:58
Just one bore of the twin damaged ? But both sides of the bore ?
The damage areas are too wide to be circlips - plus no "tram tracks" of gudgeon pin ends so I'd guess you haven't lost the circlips.
If they were NOS pistons, my guess is an undetected damaged piston...some time ago I saw a waterbus with a NOS piston which cracked right through in a very short mileage.
Were the oil ring end gaps checked ?

jellywrestler
1st September 2011, 09:45
Just one bore of the twin damaged ? But both sides of the bore ?
The damage areas are too wide to be circlips - plus no "tram tracks" of gudgeon pin ends so I'd guess you haven't lost the circlips.
If they were NOS pistons, my guess is an undetected damaged piston...some time ago I saw a waterbus with a NOS piston which cracked right through in a very short mileage.
Were the oil ring end gaps checked ?
one of the clips had come out but that was after most of the damage had occurred as there's only light scuffing. Basically I suspect the faults occurred and started to melt around the clip to release it, also these piccies are of both sides of the top of the bore, the bottom is same or worserer...
I've yet to take the front barrell off to check the piston but the bore looks OK and compression check was cool.
New made piston by OMEGA, good reputation I believe New made liner/sleeve.
Ring gaps checked? Your guess is as good as mine. I didn't rebuild this engine and have already found quite a number of simple faults with it so can't rule it out at all, of course I can't just say that'll be it and rebuild it only to find something else.
F5 Dave liner 3.67 thick, plenty thick enough i reckon

Spearfish
1st September 2011, 10:06
I'm not sure if it would be a factor for this type of damage but were the pistons facing the right way?

jellywrestler
1st September 2011, 11:15
more piccies, two are from the bottom of the barrell and the other two from the top looking down
the damage is reasonably uniform on both sides

jellywrestler
1st September 2011, 11:16
what sort of engine is this?
Vincent Twin

Paul in NZ
1st September 2011, 12:22
Combustion gasses escaping past ill fitted piston eroding the cylinder wall?

Something corrosive getting in there???

Material fault in the sleeve???

I'm a dumbarse so with something like that I'd ask the nice guys at headmaster as they do have some experience in forensic engine work.. (mostly warrenty and hire companys I think)

F5 Dave
1st September 2011, 12:28
Nah I got no idea. No clues from the underside of the piston? The rod to gungeon? Presumably these pistons are used as common fitment to vinnie engines? That is if I'm allowed to refer to them as Vinnies without some secret society hunting me down like the dog that I am:confused:

So at top & bottom centre where they should, if anything, be rocking forward & back they are brinneling out the sides but not trenching. The rod is still secure & not wobbling with crazy side to side movement?

Grumph
1st September 2011, 12:34
Drop the sleeve out - I'm betting there's no barrel where the marks are - or at least those spots will be very thin.
I've seen similar damage spots on a speedway JAP where there was a blowhole in the barrel casting - and read of the same hot spot damage on a RD Yam with a faulty barrel casting.
If this is the case I seriously doubt if that barrel is reusable. Bloody hard to get a TIG in there.

Woodman
1st September 2011, 12:50
Could be a conrod alignment issue. If the gudgeon and big end are not parallell the piston will be cocked over in the bore. From memory the specs for rod alignent are .001" difference over 6 inches, e.g. if you put a 6 inch bar through the gudgeon and another through the big end the difference between both ends should not exceed .001"

My first thoughts though were the circlips had fallen out, and I'm with Pete345673 and am a big fan of teflon buttons.

Paul in NZ
1st September 2011, 12:50
Drop the sleeve out - I'm betting there's no barrel where the marks are - or at least those spots will be very thin.
I've seen similar damage spots on a speedway JAP where there was a blowhole in the barrel casting - and read of the same hot spot damage on a RD Yam with a faulty barrel casting.
If this is the case I seriously doubt if that barrel is reusable. Bloody hard to get a TIG in there.

Ah - now we are onto something. Seen damaged bores on a resleeved hot rod triumph 650 because of this

Spearfish
1st September 2011, 20:29
If it was thin with a casting fault wouldn't it be random and look pushed out rather than looking almost like it was knocked?

Berg
2nd September 2011, 18:32
To me (mechanic by trade) that almost looks like detonation marks. Was the piston crown burnt down to the top ring area or worse on the same side? Just wonder if you are looking at a lean, too much advance, needs higher octane fuel problem.

Berg
2nd September 2011, 18:58
Yep, a good look at the photos of both the piston and liner scream "detonation".
Could be as a result of low quality fuel, too much compression or timing advance or an air leak leaning out the mixture.

bucketracer
2nd September 2011, 21:41
246087

Gudgeon pin damage seen when a circlip has been left out or come right out.


246086 246085

For what its worth, my guess is that a tang has broken off a circlip possibly by hammering from the pin due to a bent rod.

See page 10 http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

The damage is caused by the tang rattling around like a jack hammer at the ends of the stroke. The damage is both sides as the tang can rattle its way back and forth through the hollow little end pin. And the damage is wider than the gudgeon because the piston is relieved on the sides. Debris rattling around like this typically leave the piston pin hole looking melted.

Links to PDF's on Piston Damage.
http://www.boosttown.com/engine/piston_damage.pdf
http://www.ms-motor-service.es/ximages/ks_50003973-02_web_leseprobe.pdf

(http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf)

SS90
4th September 2011, 09:18
Drop the sleeve out - I'm betting there's no barrel where the marks are - or at least those spots will be very thin.
I've seen similar damage spots on a speedway JAP where there was a blowhole in the barrel casting - and read of the same hot spot damage on a RD Yam with a faulty barrel casting.
If this is the case I seriously doubt if that barrel is reusable. Bloody hard to get a TIG in there.

I have seen similar damage from this (really crap aluminum casting with big blow holes, exasperated by not using Torque plates when boring and honing........did the Engineer use Torque plates?), they are essential when lining a Cylinder in my experience, HOWEVER, The uniformness of both gouges makes me wary of saying blowholes is the problem in your case (as has been suggested by the poster above, removing the liner will give you your answer)

Infact, the fact that the gouges are even on both sides makes me suspect something is amiss with the machining of the liner (bringing back the question of if Torque plates where used or not).... It really makes me think that the bore is just not round...... As the damage is not only concentrated at 2 heights (looks like TDC and BDC) in the cylinder, but also opposite and more or less equal to each other.... If it where piston related, I would expect too see similar damage the entire length of the stroke, not just 2 points in the bore, suggesting the bore is the problem, not the piston.

I suggest you simply Mic the bore, with the Cylinder on the bench (at 3 points on the bore, from top to bottom), then, fit each cylinder to the case, make some spacers (washers will do in a pinch), the length of which are equal to the cylinder head hight, torque the cylinder down, and re mic the bore.

The difference between the two readings will reveal alot. (if the difference between
the two readings is significant, or, the Torqued down readings actually give you a "more oval reading" (with the ovality being towards the area of the damage) then you could assume the damage was caused by not boring with torque plates, or something along those lines, where as if the readings are OK, remove the liner as has been suggested, and inspect for blow holes at the points of damage, if all is well there, then logically there is a piston fault.

A correctly machined liner will be "more round" when it is torqued down, and slightly "hour glass shaped" when not torqued down.

I think you will find that a bent rod will only create excessive wear on one side of the bore, and make one hell of a racket, the first time you started it (as well as being VERY hard to turn by hand.)

The fact that the wear is NOT on the thrust faces makes me more certain there is a maching fault.

bucketracer
10th September 2011, 08:55
....... the fact that the gouges are even on both sides makes me suspect something is amiss with the machining of the liner ........The fact that the wear is NOT on the thrust faces makes me more certain there is a maching fault.

Don't think so ..............

246583 246582

The clue to this failure is in the shear symmetry of the damage, both sides of the cylinder and finishing at the ends of the piston pin travel.

Jelly there is a lot of mis-information on the net, if you want reliable information, search out authoritative tec articles like this one http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf Page 10 for pictures of a piston like yours.

Or this one http://www.boosttown.com/engine/piston_damage.pdf Page 55 for pictures of similar piston damage caused by debris trapped around the pin and page 84 for symptoms of a bent rod.

Rods are easily bent when a gudgeon pin is tapped out instead of using a pin puller when taking an old piston off. Follow the links for an explanation of how a bent rod, miss aligned little end bush or excessive side clearance on the rod or crank can lead to this sort of piston/cylinder failure buy shuttling the pin against the circlip until a piece of the clip breaks off or the clip is driven completely out.

Please post what you eventually find to be the underlying reason for this problem.

jellywrestler
13th September 2011, 17:22
After a good long read of the initial job sheet this cylinder/liner unit is one that's already done quite a bit of service.
the rear piston had failed before and the liner was cracked so the dude who rebuilt the motor had put the front back one pot.
My point is that the barrell has already been proven in service, it's not a new liner/sleeve as well as a new piston.
I heated it up today and dropped the sleeve out so will order some more bits tonight...
Thanks for all the insight into it folks, the more the merrier

SS90
14th September 2011, 08:48
Jelly there is a lot of mis-information on the net..

I totally agree, also be wary of School kids mascarading as experts, providing nothing but links to other sites.

Gigglebutton
15th September 2011, 07:45
I totally agree, also be wary of School kids mascarading as experts, providing nothing but links to other sites.

I am not sure he is the one masquerading as an expert.

Bucketracer at least knew what he was looking at and where to go to illustrate his point.

Grumph
15th September 2011, 17:47
That last is an interesting comment....remember please that those of us who have been building motors for, in my case, 41 years....don't necessarily have the computer skills you young whippersnappers do.
On the other hand we just may have seen things before....

Gigglebutton
15th September 2011, 18:06
We know he is talented because he keeps telling us ............


Thats why I build high performance two stroke engines in Europe is it... let me guess, your a...... Farmer?, no..... a waiter.... no, I got it...... A saleman for Cookie time....

And seems to know his way around the key board well enough to post supporting links for his opinions; if there were any ..........

In his last post, Jellywrestler pointed out, that "the barrell has already been proven in service, it's not a new liner/sleeve", the failure happened since a new piston was fitted.

Bucket racer suggests why the failure happened and points to places where you can evaluate his opinion for yourself, you can't ask for more than that.

SS90
15th September 2011, 20:50
We know he is talented because he keeps telling us ............



And seems to know his way around the key board well enough to post supporting links for his opinions; if there were any ..........

In his last post, Jellywrestler pointed out, that "the barrell has already been proven in service, it's not a new liner/sleeve", the failure happened since a new piston was fitted.

Bucket racer suggests why the failure happened and points to places where you can evaluate his opinion for yourself, you can't ask for more than that.

But I do build high performance two stroke engines in Europe, and have managed to feed myself off it for the last 5 years, before that, I was a motorcycle mechanic, and raced at a national championship level in 125's and 250GP..... All of tis before Kiwibiker even existed.

I am suitably qualified to question the accuracy of websites on this subject matter.

bucketracer
15th September 2011, 21:22
I am suitably qualified to question the accuracy of websites on this subject matter.

Are you sure about that.

As it seems your emphatic diagnosis of cylinder/liner distortion was a bit off the mark......

Kickaha
15th September 2011, 22:12
and raced at a national championship level in 125's and 250GP....

How many 250GP races did you do at National level?:killingme

Buckets4Me
15th September 2011, 22:17
How many 250GP races did you do at National level?:killingme


you trying to say he is lying AGAIN ?:facepalm:

well not lying so much as stretching the truth as far as posible

I've raced against 125gp's
and done 5 national gp's myself

Kickaha
15th September 2011, 22:38
you trying to say he is lying AGAIN ?:facepalm:

Not saying anything of the sort, but you only have to race a bike once in a National round to make that claim

merv
15th September 2011, 22:40
Looks like its totally been overheated which could explain the odd scalloping at the end of the stroke while the piston kind of dwells there allowing a far more localised heat buildup. Maybe it just plain melted. Now just figure out why? Oil problem? While maybe clearances were still big enough to prevent seizing.

SS90
16th September 2011, 05:25
Are you sure about that.

As it seems your emphatic diagnosis of cylinder/liner distortion was a bit off the mark......

That's only your opinion.

SS90
16th September 2011, 05:43
How many 250GP races did you do at National level?:killingme

That's the thing Warwick.... Even if I had only had one little lap, once... It would still be one lap more than these three.

Gigglebutton
16th September 2011, 07:45
Most of the posts on here were from guys relating something from their own experience and fair enough, but it looks like Bucketracer was the only one to lookup what the piston/cylinder liner manufacturers had to say about engine failures to confirm what he thought.


and raced at a national championship level in 125's and 250GP..... I am suitably qualified to question the accuracy of websites on this subject matter.

Only one ride!!!!!!! Ok it was only a little stretch.

I am not sure what the definition of “Masquerading as an Expert” is but exaggerating your qualifications has to be close.

Bucketracer may only be a School kid but has any one else noticed, he doesn’t have to BlowHard and lets the quality of his posts do the talking for him.

Latte
16th September 2011, 08:46
The wear doesn't look quite like circlip damage (at least not solely circlip damage) comparing the OP's pics and the pics supplied by BucketRacer.

Is it possible there's a lot of heat buildup coming from the little end / gudgeon area (maybe lack of oil, little end failure?). This is causing the piston to overheat around the gudgeon (as shown by the pitting/melting on the piston around the gudgeon openings) , which would have let the circlip loose.

This could also explain the wear on the barrel as the piston spends more time at TDC and BDC, causing the heat coming from the piston sides being focussed at these 2 points? I notice the damage on the barrel at these points matches the shape of the gudgeon opening.

Unfortunately I dont have years of building experience, or web pages to backup my theory... :p

SS90
16th September 2011, 08:49
Most of the posts on here were from guys relating something from their own experience and fair enough, but it looks like Bucketracer was the only one to lookup what the piston/cylinder liner manufacturers had to say about engine failures to confirm what he thought.



Only one ride!!!!!!!

Bucketracer may only be a School kid.....

I was being facetious.... I race 250's for 2 years (I owned 2 of them actually) and 125' for 4 years.

As a timely side note, there is a sticky in the title page of this thread informing all in sundry that this thread is to be kept clear of childish waffle...... Could you please bear that in mind in future post on here?
Thanks.

jellywrestler
16th September 2011, 09:47
The wear doesn't look quite like circlip damage (at least not solely circlip damage) comparing the OP's pics and the pics supplied by BucketRacer.

the difference is in the design of the piston.
The one bucket racer supplied has very little of the piston cutaway around the gudgeon pin area, whereas mine has quite a bit of releif there, the same shape of the barrell markings.
I will do a couple of piccies later today or so to show more of the piston

Crasherfromwayback
16th September 2011, 09:55
How many 250GP races did you do at National level?:killingme

And who is he anyway!!!

Gigglebutton
16th September 2011, 09:59
As a timely side note, there is a sticky in the title page of this thread informing all in sundry that this thread is to be kept clear of childish waffle...... Could you please bear that in mind in future post on here? Thanks.

SS90, looking back over your posts, it does look like your inner child was getting a bit carried away, maybe you should delete a few.


Maybe it just plain melted. Now to just figure out why?

Bucket in his posts suggested that the marks are not from the pin itself as its still retained but a piece of debris or part of a circlip has been rattling around, this typically leaves the piston looking melted in the pin area and the marks on the cylinder are more pronounced top and bottom as this is where the debris slam to a stop and both sides of the bore are marked because the offending piece of debri can pass from side to side through the hollow piston pin.

When the problem is traped debris, the marks on the bore match the cutouts in the piston and limited to the piston pin travel, his posts and links are worth a look.

This so called "melting" of the piston which is actually erosion by debri rattling around the pin area and the causes is also described by the piston manufactures in the links Bucketracer posted, I have read through them.

Jellywrestler has already ruled out there being a problem with the sleeve/cylinder so talk about sleeve machining faults and torque plates is irrelevant, the new photos will be interesting, hopefully front, back and both sides of the piston and a close look at the circlips.

Trapped debri could also be a piece of ring broken off during refitting of the cylinder, maybe a look in the sump may be in order as any trapped debri may have fallen in there when the cylinder was taken off.

husaberg
17th September 2011, 09:42
Are you sure about that.

As it seems your emphatic diagnosis of cylinder/liner distortion was a bit off the mark......

Well spotted Bucket racer
But I think SS90 is in more than his usual/unusual state of confusion. We should probably cut him a little slack as he is obviously not well.
Has anyone told him its not a scooter!!!
Although I suppose he has now kind of figured that out for himself finally.
As he as now gone on to the mopeds hence his furious backpedaling!!!!!!

Latte
17th September 2011, 10:24
Keep it on topic girls, this is actually an interesting thread :D

Interesting point about the damage, it does resemble a triple clamp where the keys have been banging against it for yeats and years, so it could be something rattling around in the side gap of the piston, instead of melting/heat.

Is it odd that both sides have the same wear? WOuld it be 2 seperate pieces, one on each side, or a single piece of debris travelling through the gudgeon? Would there be damage any damage on the inside of the gudgeon? (obviously harder material, but would be some evidence right?).

SS90
17th September 2011, 12:11
Is it odd that both sides have the same wear? WOuld it be 2 seperate pieces, one on each side, or a single piece of debris travelling through the gudgeon? Would there be damage any damage on the inside of the gudgeon? (obviously harder material, but would be some evidence right?).

Granted, but from real world experiance, my opinion is that When a cirlip comes adrift (as has been suggested) it, more often than not quite quickly ends up lodged between the piston and liner, leaving the offending item jammed in place, rather than the somewhat miraculous situation where it rattles between the two points, seemingly Perfectly in rhythm, leaving even marks at TDC and BDC.

The situation offered by others has put forward as being caused by a bent rod... My question would be, is the rod bent???

Latte
17th September 2011, 13:48
Granted, but from real world experiance, my opinion is that When a cirlip comes adrift (as has been suggested) it, more often than not quite quickly ends up lodged between the piston and liner, leaving the offending item jammed in place, rather than the somewhat miraculous situation where it rattles between the two points, seemingly Perfectly in rhythm, leaving even marks at TDC and BDC.

The situation offered by others has put forward as being caused by a bent rod... My question would be, is the rod bent???

Yes that's what I was questioning (as well as the damage on both side of the piston).

husaberg
17th September 2011, 15:03
Yes that's what I was questioning (as well as the damage on both side of the piston).

The engine damage has been sustained in only 285 miles. I doubt there is a single scenario relating to the failure but more likely a combination all of the things brought up thus far have come into play. All too often people go in search of a smoking gun when there more likely may have been more factors in play. Who built the engine,How come the engine was rebuilt, had it failed before the rebuild. Diagnosing an engine failure through pics is a little on the hard side like trying to tune a carb over the telephone. Vincent twins sure aren't that common . I do remember there being something weird/unusual in the crank float settings or such like on these engines I can remember what but it was unusual Just checked the notes- that is for the prewar singles and twins sorry.Not that it has anything to do with this the rods can also off course be twisted and the little end bush can be out of square too.From memory the Vincent twins consumed huge man hours in building them esp later on as the tooling became worn. I believe it was one of the reasons the company went broke.They were probably the most beautiful engine ever built,In one of the most technologically advanced designs for there time.The one think that struck me abot them the first time I ever got to see and hear one in the flrsh is how rately they were a lot going inside I guess lots af gears and all alloy which was rare at the time. Where's Phil (Irving)when you need him. Is Dick Hurdelman still around welly. let him have a look at it.

Jelly one of the clips had come out but that was after most of the damage had occurred as there's only light scuffing. Basically I suspect the faults occurred and started to melt around the clip to release it, also these piccies are of both sides of the top of the bore, the bottom is same or worserer...
I've yet to take the front barrell off to check the piston but the bore looks OK and compression check was cool.
New made piston by OMEGA, good reputation I believe New made liner/sleeve.
Ring gaps checked? Your guess is as good as mine. I didn't rebuild this engine and have already found quite a number of simple faults with it so can't rule it out at all, of course I can't just say that'll be it and rebuild it only to find something else.
F5 Dave liner 3.67 thick, plenty thick enough i reckon

On a short search I found this no smoking gun but relevent to the Vincent and probably other engines to.

Maughan & Sons
Vincent precision engineers
and spares manufacturer
Vincent engine barrels reboring and relining
A common thing with Vincent barrels, is that they often lose the fit between the cylinder liner and cylinder muff. There’s supposed to a 5-6 thou interference fit to ensure that the liner is snug and secure; in other words, the cylinder liner needs to have a cylinder bore 5-6 thou undersize. If the bore is too large, the liner will become loose and the clearance will be taken up by burnt engine coke.
This layer of coke, between the cylinder liner and the muff (cylinder) holds in the heat, which can result in a seized engine.
Incoming cylinders needing work are generally heated in an oven until the liner drops out. Nine times out of ten a lot of black coke comes out with it. We clean up and machine the cylinder bore, then fit an oversize liner with the correct bore size for a standard piston. Liners are made of spun cast iron, incidentally.
The final job is to hone the cylinders to finished size. This is handled by Steve who always hones the bore to near exact tolerance, and then leaves the cylinder overnight to complete in the morning. The reason for this is that things settle, not least steel. The liner protrudes a few inches from the bottom of the barrel, and this is unsupported. So it can “relax” after honing. If it does, you could end up with a piston nipping up during running-in (or even later). So the final honing is a two stage process.
This would be less of an issue in an age of less exacting tolerances. But modern machining and materials allows us to be more exacting, which has its own demands. And with pistons now running a 2-3 thou clearance, instead of 4-5 thou, you can’t afford to be sloppy
Below is an exagerated bent rod diagram

Chambers
17th September 2011, 17:06
Interesting thread.

I have read this right through from the begining including the links, but why people keep guessing when they could read what the big piston manufactureres have to say about this type of engine failure beats me, like you flick through their piston failure manuals untill you find a picture matching the failed piston and see what the piston manufacturers have to say about it, its not very hard.

Page 57 discribes what happens and lists the causes http://www.boosttown.com/engine/piston_damage.pdf


Granted, but from real world experiance, my opinion is that When a cirlip comes adrift (as has been suggested) it, more often than not quite quickly ends up lodged between the piston and liner, leaving the offending item jammed in place, rather than the somewhat miraculous situation where it rattles between the two points, seemingly Perfectly in rhythm, leaving even marks at TDC and BDC.

The situation offered by others has put forward as being caused by a bent rod... My question would be, is the rod bent???

Maybe the offending item could get jammed in place, seems sensible, but as for a miraculous situation, where it rattles between two points.

Well that is exactly what can happen according to MAHLE, AE Piston and MSI Motors as discribed in their engine failure manuals.

Now who is likely to know what they are talking about?.......

The piston manufactures, or the real life experience of someone who exaggerates his CV. :scratch: its a hard one.

A bent rod is one of the miss alignment possibilities that can hammer the piston pin into the circlip until it shatters or is dislodged and was suggested by Bucketracer as the most likely cause. As the piston was recently changed the rod could have been bent from rough handling.

And if the whole motor has been apart there are other possibilities like excessive crank float, misaligned replacement little end etc.

No doubt qualified people know this, and its OK to ask "is the rod bent???" smarter to be able to suggest an easy way to check.

Signs of a bent rod or other alignment problems are diagonal wear marks across the piston skirt. 246931


Yes that's what I was questioning (as well as the damage on both side of the piston).

This page talks about broken pieces of clip crossing to the other side of the piston 246925.

Hopefully Jelly Wrestlers new photos and investigations will tell us more.

SS90
18th September 2011, 03:49
Interesting thread.



No doubt qualified people know this, and its OK to ask "is the rod bent???" smarter to be able to suggest an easy way to check.

Signs of a bent rod or other alignment problems are diagonal wear marks across the piston skirt. 246931



This page talks about broken pieces of clip crossing to the other side of the piston [ATTACH]246925[/

I have had a short glance at this, but I am still unable to see any images even remotely like the damage shown in Jellywrestlers images, can someone point me in the right direction... Smarter to suggest ways of checking? Thats your opinion, this guy clearly has ability to remove and fit his own liners (no torque plates used, which is an engineering " No No particularly when you are dealing with a long stroke air cooled cylinder with a thick cast iron liner), so I think it is safe to assume that he has the ability to determine if how much force he is using to remove a gudgeon pin would be bending a rod (I have never personally seen a rod bent from this... I have however recently seen web based text suggesting it) and I have had to use heat and high force when removing gudgeons at different times.

I believe to bend a rod, you would have to use some force, and your average skilled home mechanic would recognize this at the time.

I HAVE however, seen damage from cylinder machining faults, on an engine run for about 20 dyno runs, and showing signs not too dissimilar to Jellywrestlers pictures.... However, the wear was no where near as much as he has, but similar in position for sure.

bucketracer
18th September 2011, 08:36
One of my suggestions was, a broken clip has caused the damage, and a bent rod is only one of the reasons a clip can be broken or ejected.


put forward as being caused by a bent rod... My question would be, is the rod bent???

A more telling question would have been " is there a clip or part of one missing?".

Woodman
18th September 2011, 09:38
It does not take much force to bend a con rod at all. The bent rod thing may be that the big end and small end are not in alignment. This can be either laterally or it could be twisted meaning the small end will travel along the gudgeon pin and back every stroke. Couple this with not much rod to boss clearance and possibly the rod is pushing the piston against the cylinder wall each time it reaches tdc or bdc.

The rod could also be perfectly aligned but the rebore could have been done on an angle which has similar symptoms. Easy to check all this on a conventional engine where you can assemble it and turn it over and see whether the small end "walks" along the pin as you turn it over. Hard to check on a motorcycle engine though.

BTW these are just theories from the pics that I can see. So don't start a shit fight.

husaberg
18th September 2011, 12:39
One of my suggestions was, a broken clip has caused the damage, and a bent rod is only one of the reasons a clip can be broken or ejected.

A more telling question would have been " is there a clip or part of one missing?".

I think the foreign corespondent has missed the engine has just been rebuilt bit. It was obviously rebuilt for a reason by person unknown for unknown reasons.In fact I wonder if ther e could be some form of out of parrellel in the case or bearing and or sleeve as well. Like I said earlier everyone always looks for a smoking gun when it could be a whole series of problems.

jellywrestler
18th September 2011, 17:50
took the front barrell piston off and here's the comparison between the two...

bucketracer
18th September 2011, 17:56
Good pictures, and plenty of shrapnel there.

246996

Does your damaged piston look like picture 1.1.2 in the PDF, it does to me.

This is my take on it, the damaged piston is starting to develop the classic melted piston look in the piston pin area from debris being shaken up and down. Eroding the piston and marking the cylinder at the end of the pin travel as they slam to a stop at each end of the stroke. The clip and debris were not able to escape the piston cutout and were held there and shaken up like they were in a cocktail shaker.

246999

This all started with the piston pin clip coming out. The clip was trapped in the piston cutaway area and couldn’t escape or become trapped in a transfer port like it might in a 2-Stroke. As it was shaken violently up and down it eventually broke up the oil control land and ring releasing debris that marked the bore, the marks are both sides as the debris can travel to the other side of the piston through the hollow piston pin. The piston pin did not leave the classic tramlines, maybe there was not enough time or its ends just did not dig into the bore.

247002 TDC 247003 BDC

The shrapnel damage evidence, is in the symmetry of the markings on the cylinder wall matching the piston cut outs, on both sides and at TDC and BDC. Curved at TDC matching the pin cutout in the piston and straight at BDC matching the straight bottom of the piston cutout. And finishing at the exact extremes of the piston cutouts travel. I expect if you put the piston in the bore the damage will exactly match the cutouts at TDC and BDC.

The clip may not have been fitted properly or was being hammered by the piston pin due to a miss alignment problem and ejected, further investigation of the damaged piston can reveal which.

247000 247001

If there is a miss alignment problem it will show in a diagonal wear pattern on the damaged piston. Typically the top on one side and the bottom on the other side touches the bore and there is diagonal wear lines between them on the thrust sides of the piston skirt. With such a low mileage it may be hard to see but if its there, there should be some indication.

I would be quite keen to see photos of the thrust sides of the pistons if possible.

Crasherfromwayback
18th September 2011, 18:15
took the front barrell piston off and here's the comparison between the two...

Some pretty serious heat going on there!

Grumph
18th September 2011, 19:28
Is the more severely damaged side, the plug side ?

Buckets4Me
18th September 2011, 22:11
Piston Damage

On both sides of the piston, the end of the piston pin bore has suffered serious damage. In some places the damage reaches up as far as the ring zone (Fig. 1).



When the piston was removed there was no longer a circlip in the retaining groove. It had jumped out during operation and broken into fragments. Although the second circlip is damaged, it was still installed in its groove when the piston was removed. Due to the lack of retention, the piston pin has wandered outwards during operation towards the cylinder running surface. Clearly the front face of the pin has prolonged contact with the cylinder running surface. As a result, the front face is worn to a convexed shape (Fig. 3). The running pattern of the piston is formed very asymmetrically.




247036



just a scrape from the web (may or may not be relavent) but the damage was not caused from heat

Chambers
18th September 2011, 22:27
(no torque plates used, which is an engineering " No No particularly when you are dealing with a long stroke air cooled cylinder with a thick cast iron liner)

A No No?????

No doubt Torque Plates are a great idea and I am a bit of a believer. But I don't think they are that common and there has been a lot of good engineering done without them. I don’t recall them being required by my 1948 copy of Modern Motorcycle Mechanics that hails from the era of the Vincent or any of the more modern motorcycle workshop manuals that I have seen.

If there are any factory workshop manuals for common modern road bikes of any era or even an exotic one that insists on a Torque Plate during rebuilding/reboring/reconditioning I would truly love to see a quality post about it complete with a PDF scan and/or a link or two.

Chambers
18th September 2011, 22:42
246996

Does your damaged piston look like picture 1.1.2 in the PDF, it does to me.

I expect if you put the piston in the bore the damage will exactly match the cutouts at TDC and BDC.

Two very good points.

Point-1) Does the damaged piston look like the 1,1,2 one in the PDF??

Point-2) And does the marks in the bore on both sides match the piston cut outs at TDC and BDC??

Hopefully Mr Jelly will take a look and tell us.

This is very interesting. :yes: as point-2 in particular could make or break Buckets theory.

Gigglebutton
19th September 2011, 09:55
246996

Does your damaged piston look like picture 1.1.2 in the PDF, it does to me.

The shrapnel damage evidence, is in the symmetry of the markings on the cylinder wall matching the piston cut outs, on both sides and at TDC and BDC. Curved at TDC matching the pin cutout in the piston and straight at BDC matching the straight bottom of the piston cutout. And finishing at the exact extremes of the piston cutouts travel.

{if I am right} I expect if you put the piston in the bore the damage will exactly match the cutouts at TDC and BDC.

A 7th Form school boy doing the research and asking the right questions, puts us "Real World Experts" to shame, one way or the other, its good work and thinking Bucketracer.

speedpro
19th September 2011, 21:12
Another thing to look for is the piston pin circlip grooves being distorted where the gudgeon pin may have been trying to push it out. I've seen it where the grooves were nearly twice as wide as original.
Teflon buttons are great. So much easier to get in and out, as long as they don't fall in the sump when you lift the barrels off.
I made a 40mm thick surface ground torque plate for my turbo engine barrel. The bloody engine reconditioners took the barrel off the plate to bore it, which unfortunately for them I noticed. I had it measured by some real engineers in their climate controlled measuring room. The bores were all straight and parallel, individually, but the cylinder block had a slight twist, hence the big plate to bolt it to. The end result was the two bores had a very slight slope forward and the other two sloped ever so slightly backwards when it was all bolted down on the plate.
Grooves in the barrel from a pin getting out the side of a piston probably won't be even because of the offset. The gudgeon pin hole in the piston will not be in the centre.
The damage is definitely caused by a bit of debris rattling around.

Buckets4Me
19th September 2011, 21:26
Granted, but from real world experiance, my opinion is that When a cirlip comes adrift (as has been suggested) it, more often than not quite quickly ends up lodged between the piston and liner, leaving the offending item jammed in place, rather than the somewhat miraculous situation where it rattles between the two points, seemingly Perfectly in rhythm, leaving even marks at TDC and BDC.




how would the clip get between the piston and barrel? As the ring normaly scrapes the oil off the barrel and the gas from under the cylinder head cant get past either.

Remeber this is a 4 stroke not a pesky 2 stroke scooter with ports everywhere for the clip to jump into :facepalm:

there is however a big cavern where the little end pin is that the clip can rattle around in

and being that it will be draged up and down the barrel anywhere up to 8000 times a min. there is a good posibility that it will leave lots of marks up and down the liner (specialy at the top and bottom of the stroke)
also anyparts of the piston or rings that it can brake off then start to traveling up and down with it (also causing damage)
this damage will be more at the top and bottom of the stroke (where everything changes direction)

as for even marks at tdc and bdc
logic says the piston goes up and down more or less the same amount of times leaving more or less the same amount of damage at both the top and bottom of the stroke

TZ350
20th September 2011, 16:20
It does not take much force to bend a con rod at all. The bent rod thing may be that the big end and small end are not in alignment. This can be either laterally or it could be twisted meaning the small end will travel along the gudgeon pin and back every stroke. Couple this with not much rod to boss clearance and possibly the rod is pushing the piston against the cylinder wall each time it reaches tdc or bdc.

The rod could also be perfectly aligned but the rebore could have been done on an angle which has similar symptoms. Easy to check all this on a conventional engine where you can assemble it and turn it over and see whether the small end "walks" along the pin as you turn it over. Hard to check on a motorcycle engine though.

Yes, agreed, rods are easily bent and if there is any miss alignment you can see the pin walking when looking up inside a reco car/truck motor while turning it over.

Another way of checking for a bent rod is to slide a feeler gauge around the top of the piston at TDC, a bent rod will show up as being tighter on one side than the other. This can be done on the Vincent if the barrel is held down.

You can also check for broken rings this way too as the tip of the feeler gauge will drop into the gap where a piece of ring is broken away. You can also check the other compression and oil rings too by pushing the feeler gauge down past each ring in turn then sliding the feeler around to see if there are any gaps.

Gigglebutton
20th September 2011, 18:01
247139 Mr Jellys blown Vincent piston.


I am still unable to see any images even remotely like the damage shown in Jellywrestlers images, can someone point me in the right direction...


PDF 246996

picture 1.1.2 in the PDF,

There you have it ... and I see it says "Damage caused by circlip"

TZ350
20th September 2011, 21:00
my opinion is that When a cirlip comes adrift (as has been suggested) it, more often than not quite quickly ends up lodged between the piston and liner, leaving the offending item jammed in place,

rather than the somewhat miraculous situation where it rattles between the two points, seemingly Perfectly in rhythm, leaving even marks at TDC and BDC.

The situation offered by others has put forward as being caused by a bent rod... My question would be, is the rod bent???

Picture 1.1.1 and 1.1.2 show both sides of the same piston with damage on both sides from one lost circlip and it looks very much like Jellywrestlers piston.

On the same page is a list of possible causes for the clip coming out, and a bent rod is one of them.

None of the piston failure pictures (all 4 stroke) from any of the piston makers manuals showed a clip jamed between the piston and liner, so a jamed clip is probably not that common in a 4 stroke, maybe more a 2 stroke thing.




246996 Does (the) damaged piston look like picture 1.1.2 in the PDF, it does to me.

Spearfish
20th September 2011, 21:13
progress!

aye?

jonbuoy
21st September 2011, 03:00
Looks like the damage started below the oil rings and worked its way up, fair amount of material missing around that area. Points more to Cir-clip than anything else I could hazard a guess at, carbon hasnīt even been wiped off the side of the crown above the first compression ring.

SS90
21st September 2011, 08:26
Picture 1.1.1 and 1.1.2 show both sides of the same piston with damage on both sides from one lost circlip and it looks very much like Jellywrestlers piston.

On the same page is a list of possible causes for the clip coming out, and a bent rod is one of them.

None of the piston failure pictures (all 4 stroke) from any of the piston makers manuals showed a clip jamed between the piston and liner, so a jamed clip is probably not that common in a 4 stroke, maybe more a 2 stroke thing.

That is your Google search, internet based assessment, and, you are entitled to have it, I'm not trying to take it from you.

Decades of experience have shown me that relying on web based text is, more often than not, misleading.

Just because it is not on the web does not mean it does not happen TeeZee.

I have seen circlip failures, both on Four and Two stroke engines, all with varying degrees of damage, including circlips wedged between pistons and liners.

The forces involved can and do create mechanical mayhem beyond what most people realise., I have seen 20 odd horsepower engine disintegrate high quality pistons like they where glass, and bend rods 90 degrees, and 100+ horsepower engines simply crack a piston, and simply stop running.

The engine we are talking about has suffered a mechanical failure, I remain unconvinced that it was caused by a bent rod, not the least of which is due to the fact that common sense tells me that the owner/assembler has the "wear with it all" to be able to identiify when too much force is being exerted on the rod when removing the piston originally, so far, he has remained silent on this issue, perhaps he can shed some light.

I cannot remember a circlip breaking off just one section, and am struggling to think of a situation that would cause just one section to break off, ,particularly if as your 2 sons, employer and yourself maintain, if a bent rod was to blame... IF (again, not my opinion) a bent rod caused the gudgeon to apply sideways force against the circlip, would the whole clip not come out (there is room, as the cut away above the gudgeon pin hole does appear big enough to accommodate a complete circlip, and I cannot see how a circlip would just shatter of it's own accord... They normally are made of spring steel (but actually we have not seen an image of the type of clip fitted)

I assemble engines every day, and on occasion I have found that a piston can be, for varying reasons, an interference fit on the gudgeon, and, more often than not, I need to heat the piston to remove the gudgeon (some older competition part manufactures actually specify an over size gudgeon, requiring matched sets, but these are pretty rare in my experience).

I seem to recall some manufacturers in such situations instruct the technician to heat the piston in oil before assembly, but have never seen anyone adhere to this technique, instead using either a heat gun, or butane torch, does this mean not heating it in oil is wrong, when it is industry standard to use another method?

That said, there have been situations that, for what ever reason (at the track, no gudgeon removal drift), I have had to "encourage" a stubborn gudgeon from a piston, involving some fairly unsexy bashing of the assembly, and, to date, no bent rods, ever.

Is is where Internet information, and real world situations differ, when you actually do it, and, as such have the experience, rather than just the theory, you learn for yourself what is correct.

Many is the spotty little kid that comes into a workshop, fresh from his education, that soon, with in a month realises the difference between the theory and experience is massive.

F5 Dave
21st September 2011, 09:18
. ..
Decades of experience have shown me that relying on web based text is, more often than not, misleading. . .

Gee you must have had the internet longer than the rest of us.

Spearfish
21st September 2011, 09:25
Surly this all could be sorted when the cases are split and the old wooden measuring stick gets a workout checking to see if things are as a guy with a wooden measuring stick, pencil and an abacus intended to be at the engines inception?

Crasherfromwayback
21st September 2011, 10:07
Is is where Internet information, and real world situations differ, when you actually do it, and, as such have the experience, rather than just the theory, you learn for yourself what is correct.

Many is the spotty little kid that comes into a workshop, fresh from his education, that soon, with in a month realises the difference between the theory and experience is massive.

You're full of yourself. And the day I see a clip get between the piston and the cyl wall on a four stroke is the day I'll apologize.

SS90
21st September 2011, 10:31
You're full of yourself. And the day I see a clip get between the piston and the cyl wall on a four stroke is the day I'll apologize.

Well (your majesty), may I direct you to the very page that these guys refer to

http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

Page 10 to be correct.

Does that look like a circlip has lodged in between the piston and the liner?

You don't need to apologise......

actungbaby
21st September 2011, 10:35
Thats alot damage looks to me the guedion pin damage for sure esp the shape of the marks and damage to the piston also . was there to much clearance in the bore unless you didnt but new circlips in for the pin or where not in the groove
bad luck dude did you stagger the pistion rings also so gaps where lined up

postive side can be fixed



just pulled a barrel off and found some lovely marks in it, these are both sides of the barrel and there's similar marks at the bottom.
From the top the piston looks all good but has started to go bad on the sides particularly above the gudgeon pin area, rings are had it.
285 miles on a new sleeve and piston it's a twin cylinder two carbs what went wrong?

bogan
21st September 2011, 10:44
Well (your majesty), may I direct you to the very page that these guys refer to

http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

Page 10 to be correct.

Does that look like a circlip has lodged in between the piston and the liner?

You don't need to apologise......

Kind of looks like the clip has bounced around but consistently hit the top side in the same orientation. :dodge: Would expect more definitive marks if it lodged in there.

Crasherfromwayback
21st September 2011, 10:45
Well (your majesty), may I direct you to the very page that these guys refer to

http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

Page 10 to be correct.

Does that look like a circlip has lodged in between the piston and the liner?

You don't need to apologise......

For someone that rubbishes the internet compared to your vast knowledge...I'm freaked out you'd refer me to the internet!

And not really.

Having long ago been a mechanic by trade and having worked as one in the rental car industry...then in the bike industry for 25 years...I've yet to see myself, a circlip get between the piston and the cyl wall of a four stroke. Maybe once the piston and cyl are destroyed enough so there's room for it to escape...but not in the first place that's caused the original damage.

I would say...you're simply a sore loser that's been out smarted by a bright youngin, and don't have the decency to admit it.

SS90
21st September 2011, 10:52
And not really.

amage.

I would say...you're simply a sore loser that's been out smarted by a bright youngin, and don't have the decency to admit it.

Those that live in glass houses...........

Crasherfromwayback
21st September 2011, 10:54
Those that live in glass houses...........

Should wear clothes?

TZ350
21st September 2011, 11:52
Does that look like a circlip has lodged in between the piston and the liner?

You don't need to apologise......

http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

Page 10 to be correct.

No, .... a fretted imprint maybe and a very good example of what Bucket has been talking about.

247179 Click the picture to read the text.

SS90 this is the page you quote in your reference, and no doubt its the combined real life experiance of a lot of people who work in the automotive industry who have analysed many engine failures and determined their cause.

Now tell me, does your page say melted appearance and misaligned (bent) rod as a possible cause just like Bucket has been saying, yes it does.

And do you see any reference to a jammed clip, nope you don't do you.

jellywrestler
21st September 2011, 12:15
Those that live in glass houses........... should have sex in the basement...

tri boy
21st September 2011, 13:33
All of the preceding comments on the possible cause of the damage is exactly that, possible.
The probable cause is the Jellyman.
He can f**k a yellow bellied black snake, even if nobody is holding it head.:shutup:

FastFred
21st September 2011, 20:39
it sounds like
someone is so stupid...they would inserted a window in a glass house!:-)

:yes:

now lets wait and see if the rod is bent or not

but remember a bent rod is only one reason for it to happen
can we name 3 more ?

Ned Kelly
21st September 2011, 20:53
Those that live in glass houses...........

Should throw stones, but Keith Richards is much tougher to throw than Mick Jagger.

bucketracer
21st September 2011, 22:12
That is your Google search, internet based assessment, and, ........ Many is the spotty little kid that comes into a workshop, fresh from his education,

Your being really silly now .......

husaberg
21st September 2011, 22:14
Those that live in glass houses...........

should have great vege garden?

Should not smoke their own poppies?

Should give up when they are clearly wrong?

Should not post pictures of themselves on the net?

Should admit defeat when they are clearly out witted?

Should move to Europe and not feel the need to keep in touch?

Should aspire to be a scooter tuner in a country, without an extradition treaty with NZ?

Should not try and keep exaggerating there resume's when people in NZ have long memories?

speedpro
21st September 2011, 22:22
There are clips with the little tangs you can grab with pliers to insert or remove the clips. I have seen where a pin had been pushing and rubbing on a tang to the point where the little tang broke off. Probably why clips nowadays don't have tangs sticking up.

bucketracer
21st September 2011, 22:35
There are clips with the little tangs you can grab with pliers to insert or remove the clips. I have seen where a pin had been pushing and rubbing on a tang to the point where the little tang broke off. Probably why clips nowadays don't have tangs sticking up.

247204

Dad says these were a real problem in TZ's as they would be cut through by the pin and break off damaging the engine. It was std practice to cut them off first when fitting new pistons.

husaberg
21st September 2011, 22:45
247204

Dad says these were a real problem in TZ's they would be cut through by the pin and break off damaging the engine. It was std practice to cut them off when fitting new pistons.

There use to be the square ended ones too. I can't be arsed looking for a pic but they looked like a gearbox circlip holes and all. Well maybe I can.
But i guess the new piston that were in jelly's motor would have modern design circlips.
Did jelly find the remains of 1 or 2 circlips in the cases?
Mistakes can happen to the best of us sometimes.:innocent:

Buckets4Me
22nd September 2011, 19:26
Interesting point about the damage, it does resemble a triple clamp where the keys have been banging against it for yeats and years, so it could be something rattling around in the side gap of the piston, instead of melting/heat.

Is it odd that both sides have the same wear? WOuld it be 2 seperate pieces, one on each side, or a single piece of debris travelling through the gudgeon? Would there be damage any damage on the inside of the gudgeon? .

probably many pieces. if you look at what is left of the rings you will notice that there is a fair bit missing. And some of those bits are likely to find there way threw the pin (as thats much easier than betwen the piston and cylinder) you have the same thing happening both sides of the piston.

one side of the piston has more damage than the other
so I would like to know if the missing clip came from that side or not ?
and is the rod bent or not ?

if the rod is bent then why
and if it isn't then what made the clip come out ?

if the rod isn't bent then was there a broken ring ( looking at the pics I cant tell where it could have been broken ) or was there some material on in or around the little end pin?

jellywrestler
22nd September 2011, 19:40
one side of the piston has more damage than the other
so I would like to know if the missing clip came from that side or not ?
and is the rod bent or not ?


There was only one circlip 'missing' well i found a third of it intact the rest had long gone.
the greater damage was on the side where the clip was out This is logical as teh clip would've hung around here in larger bits before breaking up and some travelling to the other side.
i made a Mandrel up to check the rod and am happy it's not bent.
Pressing the gudgeon out was done with a tool onto the piston so there was no forces in this process at all travelling down the rod, besides the gudgeoans were a little more than finger tight

Buckets4Me
22nd September 2011, 19:45
to much end float on the crank ?
or side clearance on the big end
or twisted rod
is more posibilities

or someone missfited the clip :facepalm: this may be why speedpro DOSEN'T reuse clips

husaberg
22nd September 2011, 19:55
[/URL]
to much end float on the crank ?
or side clearance on the big end
or twisted rod
is more posibilities

or someone missfited the clip :facepalm: this may be why speedpro DOSEN'T reuse clips
Sorry no Vespa pics here Neil
The rod bushing can be machined not square resembling the symptoms of rod misalignment

I found these pics and threads
http://www.foxwooddiesel.com/piston-damage-circlip
[url]http://www.k20a.org/forum/showthread.php?t=41515 (http://www.k20a.org/forum/showthread.php?t=41515)
http://www.rallyanarchy.com/phorum/read.php?5,1989,2047
http://www.hadmac.com/piston_&liner.htm


Shhh...I don't think we are allowed to talk about speedpros circlips, as well as his conrod. It is a secret still after-all.
And sorry to keep you waiting Buckets4me one of the kids called out.

Buckets4Me
22nd September 2011, 20:01
I found these pics and threads


pics and thread ????

I'll come back in half an hour and re read that post and see if I can understand it better
:yes:

thats better

TZ350
22nd September 2011, 22:06
Real life experience or something from the net that Bucket clued me into ........ well who knows ... :laugh:

Here is a very easy way of checking for a bent rod. Its such a useful assembly check I am surprised someone else with a lot of industry experiance hasn't mentioned it.

247251

Hold the barrel down and then with the piston at TDC slide a feeler gauge around the top, if the rod is even slightly bent it will be tighter on one side than the other. When I was working a lot with engines, this was a standard test done on every cylinder as a double check for alignment issues. You could also feel for broken rings this way too.

Circlips were always given a half turn in their grooves to be sure they were properly seated and there was no forgien matter caught behind them. If the clip was not properly in its grove when you turned it you would hear it click into place.

Turning the clips, now thats another industry trick that someone in the know could have told us about too.

TZ350
22nd September 2011, 22:29
There was only one circlip 'missing' well i found a third of it intact the rest had long gone.

Is there any sign in the grove that the pin has been hammering the clip?

jellywrestler
22nd September 2011, 23:04
Is there any sign in the grove that the pin has been hammering the clip?
no i checked for that.
the bike run for aeons with the previous piston etc in it and with a mandrel i made fitted sits on the cases sqare both sides.
I did find the circlip in the front piston installed in a poor place. ie the end of the clip was in the relived area used for flicking the clip out, whereas it should be held in better, just poor trade practice really...

TZ350
23rd September 2011, 03:12
Square across the cases, that’s a good way of doing it.

No hammering, nothing out of align, then pointing towards poor installation? Bummer

Grumph
23rd September 2011, 07:17
Out of curiosity Mr Jelly, two quesions -
Again, was the more heavily damaged side, the plug side ?
And, when the front barrel was moved to the rear position, did the oilways line up ?

Thank you - and I hope you've learned from all this, never put "dramas" in a thread title, look at the angst you've caused......

husaberg
23rd September 2011, 21:16
Out of curiosity Mr Jelly, two quesions -
Again, was the more heavily damaged side, the plug side ?
And, when the front barrel was moved to the rear position, did the oilways line up ?

Thank you - and I hope you've learned from all this, never put "dramas" in a thread title, look at the angst you've caused......

Drama and angst.You make it sound like a teenage soap.

I want my money back cause where's the hot looking chick with daddy issues? I want a boob shot. Or was that Neil?
Cause if thats the case I want my money back. We did get the cat fight though.

pete376403
23rd September 2011, 22:06
Post #3 appears to be first correct answer, what do I win?

husaberg
23rd September 2011, 22:29
no i checked for that.
the bike run for aeons with the previous piston etc in it and with a mandrel i made fitted sits on the cases sqare both sides.
I did find the circlip in the front piston installed in a poor place. ie the end of the clip was in the relived area used for flicking the clip out, whereas it should be held in better, just poor trade practice really...

Mr Jelly I googled the VOC (Vincent owner Club) site
"problem with Omega pistons VOC" should do it for you.
There is a write up somewhere on the site problems with Omega pistons
For some reason my computer won't access it as I think it has the flu or something
but have a look there and see what you find.

PS have you considered turning the Rapid into a Comet or better yet a Gray Flash? You are already half way there.:weep:

pete376403
23rd September 2011, 22:53
Omega are (were) a recognised brand back in the day when I was racing speedway. My Weslake had an Omega, of all the problems that motor had, the piston wasn't one of them, and I'd suggest a speedway motor running at full tit is a bit more stressed than a Vincent on the road. But, as I mentioned before, I didn't use circlips, preferring teflon buttons (a wee bit heavier, but a shitload more reliable)

husaberg
23rd September 2011, 23:28
Omega are (were) a recognised brand back in the day when I was racing speedway. My Weslake had an Omega, of all the problems that motor had, the piston wasn't one of them, and I'd suggest a speedway motor running at full tit is a bit more stressed than a Vincent on the road. But, as I mentioned before, I didn't use circlips, preferring teflon buttons (a wee bit heavier, but a shitload more reliable)

Re Omegas
They still are and I have heard only great things about them.
What does the write up say?
I don't know
Your piston/s were presumably forged. Are Jelly's I don't think they are by the look of them.Edit the pic one page back defiantly ain't forged.
The Britten ran Omega amongst others F1(Well the Blanks were).
For all I know the piston may have been done on a Friday, the manufacture may have been shipped offshore,They may have been roughly handled.The piston may have had an old circlip put in by mistake.There could have been a bad batch of circlips or just one.

Found this toohttp://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=236715

Buckets4Me
25th September 2011, 09:48
gudgeon pin circlip come out?



sounds like you where first to come up with it

and thats not a piston fault :facepalm:

Spearfish
25th September 2011, 10:49
All that happened from not getting the wee little clip fitted home properly or using the old ones.

At least the ones in the thread swinging handbags were standing up while the rest were sitting. Shits and giggles.

bucketracer
25th September 2011, 12:41
Real life experience or something from the net that Bucket clued me into ........ well who knows ... :laugh:

Here is a very easy way of checking for a bent rod. Its such a useful assembly check I am surprised a certain someone else with a lot of industry experience hasn't mentioned it.

247390

Hold the barrel down and then with the piston at TDC slide a feeler gauge around the top, if the rod is even slightly bent it will be tighter on one side than the other. When I was working a lot with engines, this was a standard test done on every cylinder as a double check for alignment issues. You could also feel for broken rings this way too.

And circlips were always given a half turn in their grooves to be sure they were properly seated and there was no foreign matter caught behind them. If the clip was not properly in its groove when you turned it you would hear it click into place.

Turning the clips, now thats another industry trick that someone in the know could have told us about too.


There was only one circlip 'missing' well i found a third of it intact the rest had long gone. The greater damage was on the side where the clip was out This is logical as teh clip would've hung around here in larger bits before breaking up and some travelling to the other side.


All that happened from not getting the wee little clip fitted home properly or using the old ones.

Dad tells me that its pretty easy to crush this type of circlip out of its round shape into an oval when fitting it, clips bent even slightly oval are weaker and don't have the right shape to withstand the accelerative forces at the end of the stroke and can easily pop out of their groove.

247391


As well as pictures of various types of piston damage and their causes, distortion of circlips when fitting is talked about in at least one of the links to the engine failure manuals that I posted.


I am still unable to see any images even remotely like ... can someone point me in the right direction ...

SS90 if you can't find it, I will be happy to point it out, as a bit of reading can save even the wisest man from repeating his mistakes.

jellywrestler
25th September 2011, 20:39
Here's something else, there are two different size clips for the gudgeon pin, 54 thou and 64 thou, the 64thou ones being in the damaged piston and are a smaller 'loose' size
IE they nearly drop into the hole, not bugger all spring tension to make sure they are held in in my mind now either the two pistons have differnt size clip grooves or the builders simply put some clips in that are fatter than they need be and were never going to fit in the groove...
The broken peice is all that was left of the offending clip

TZ350
25th September 2011, 20:44
Different clip diameters, well I wasn't expecting that, they look like they were meant for different size pins.

And I wonder if there is a std imperial and metric circlip wire thats close to the same size, I hadn't thought about it before but it seems probable now.

The clips for the Kawasaki and Wiesco pistons I use in my bike are made from different size circlip wire, at a quick glance the clips look the same and they are the same diameter. But I have to be careful not to mix them up as they don't sit down properly in the grooves if I do. I hadn't thought about the reasons, I was just careful.

Very interesting and well done, looks like you have found the smoking gun.

husaberg
27th September 2011, 15:52
:wait:
Different clip diameters, well I wasn't expecting that, they look like they were meant for different size pins.

And I wonder if there is a std imperial and metric circlip wire thats close to the same size, I hadn't thought about it before but it seems probable now.

The clips for the Kawasaki and Wiesco pistons I use in my bike are made from different size circlip wire, at a quick glance the clips look the same and they are the same diameter. But I have to be careful not to mix them up as they don't sit down properly in the grooves if I do. I hadn't thought about the reasons, I was just careful.
Very interesting and well done, looks like you have found the smoking gun.

I posted this earlier about circlips, Links below
Who knew there were so much intricacies involved with them. I sure didn't
A one dollar part that has the potential for so much Heartache.
No doubt someone probably has written a doctorate thesis on them at some stage.:shutup:

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=236715
http://kb-silvolite.com/article.php?action=read&A_id=54

Re the smoking gun

the evidence has found what appears to be the weapon. But:wait:
Who fired it :ar15:

Was it a mistake at the factory by placing the wrong circlips with the piston.
compounded by the fitter not recognising the problem, or not checking at fitting?:innocent:

Or a mistake by the fitter using the wrong clip ?:o

In the pic I did note the hatch pattern looked a little odd to as it was to lack a better description asymmetrical one sided weird, It might be the angle of the pics.But it seems inconsistent.I wonder why.

husaberg
29th September 2011, 17:27
Here's something else, there are two different size clips for the gudgeon pin, 54 thou and 64 thou, the 64thou ones being in the damaged piston and are a smaller 'loose' size
IE they nearly drop into the hole, not bugger all spring tension to make sure they are held in in my mind now either the two pistons have different size clip grooves or the builders simply put some clips in that are fatter than they need be and were never going to fit in the groove...
The broken piece is all that was left of the offending clip

I did come across this little gem in Phil Irvings Tuning for speed. It makes a lot of sense to with regards to the shape of the pin. Clever bloke that Phil.

bucketracer
29th September 2011, 17:32
That's pretty good value ...........

bucketracer
1st October 2011, 14:44
That is your Google search, internet based assessment ....... Many is the spotty little kid that comes into a workshop, fresh from his education, that soon realises the difference between the theory and experience is massive.

What you say is true, although not nice or very smart.

I have spent a lot of time with Team ESE in the workshop and know my limits but I am smart enough to do some research and join the dots, so in my posts as well as writing about what I have learn t, I like to research and reference other people with real industry experience and something credible to say, if I get stuck and ask, TeeZee or Thomas will always point me in the right direction.

Pictures of TeeZee's 239 hp per liter FZR/GP125 Bucket with a good 3,500rpm power spread, I helped with a lot of the work developing it.