FXR150 conrods breaking

[Sideways Sam]

We just broke a conrod on our bike, put a hole right through the crankcase. One day later Dangerous did the same thing to his engine. This is the third conrod break I know of on one of these engines in the last month or so. I've also heard of a lot of others through the grapevine.

It would appear that this is a weak point in these engines so I'd like to hear from anybody else that has had a similar incident. We had increased the compression on our bike which wouldn't have helped but the rod lasted less than an hour!!!!!

If anybody who has had a similar problem could post details, particularly:
Compression Ratio
What engine was doing at time of failure (revs etc)
other mods

I realise that most of you won't want to admit to your mods in case somebody copies them but the truth is most of the races I've seen are currently being won by stock engines........ These things are breaking regularly and it would be in everybodiy's best interests to find the source of the problem so that we can build reliable engines (I'm currently looking into getting Wiseco to make a batch of rods for these things)

I'd also be interested to hear from anybody regarding seizures and the circumstances surrounding them.

[Kickaha]

(I'm currently looking into getting Wiseco to make a batch of rods for these things).

Why not use stock rods and get them shot peened

Where are the rods breaking, are they all doing it in the same place?

[bucketracer]

You Guys should give up on those fussy, fragile, heavy, difficult to maintain, expensive, performance limited, technically complicated 4 smokes and go with one of those strong reliable, light, quick, easy to work on 2 strokes that have loads of performance potential. :bleh:

[Pumba]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.

[Mrs Busa Pete]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.

That's because your's is standard.

[Sideways Sam]

Why not use stock rods and get them shot peened

Where are the rods breaking, are they all doing it in the same place?
Damn fine idea, I'd already thought of shot peening, I'm not sure it's going to make the difference we need though.

The mods I had made to my engine were turning out an estimated 35% increase which is a lot more stress on everything. Some of the bike that are dropping rods are stock standard.....

Does anybody know how much shot peening can do to stregthen a rod?

[Sideways Sam]

Bugger, wasnt such a good Taupo then.

Ive had no issues, but I will be watching with interest.
Taupo was great, would've been a hell of a lot better if we had a bike that went though!!!!

Spent the time on the recover vehicle peeling bikes off the track and sweeping up oil......... Bloody classics..........

[Sideways Sam]

You Guys should give up on those fussy, fragile, heavy, difficult to maintain, expensive, performance limited, technically complicated 4 smokes and go with one of those strong reliable, light, quick, easy to work on 2 strokes that have loads of performance potential. :bleh:
I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.

[Buckets4Me]

W(I'm currently looking into getting Wiseco to make a batch of rods for these things)


not in the rules is it
I wasnt allowed to use Bousen reeds :argue:

got to be a stock rod as I have been told by the welly crew
or its not in the spirit or rules

[Buckets4Me]

I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.

the number 1 plate is on a 2 stroke that broke on saturday and would have won easily like it did last year

it's all in the rider and bike
plus the 4 strokers need more cc's to compeat and they dont get the handycaps the 2 strokers get

[Sideways Sam]

not in the rules is it
I wasnt allowed to use Bousen reeds :argue:

got to be a stock rod as I have been told by the welly crew
or its not in the spirit or rules
It's a mute point in the rules

"Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve
springs or cooling system except for class eligibility."

It depends if it's classified as a transmission part or not. As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I'm sure that JC's 125 twins (the fast ones anyway) aren't running stock rods etc.......

If it's OK to change the piston, surely it's OK to change the rod?

This will be an interesting discussion!!!!!!

[Sideways Sam]

I've just had confirmation from a guy that's done 2 big ends:

One was due to a gudgeon pin clip getting loose and making it downhill to get in the way of the big end

The other was probably stuffed before he bought the bike

[Kickaha]

As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I

The rod I got from them was a Suzuki rod, there's nothing special about them

[Buckets4Me]

It's a mute point in the rules

"Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts are not permitted. There shall be no restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve
springs or cooling system except for class eligibility."

It depends if it's classified as a transmission part or not. As far as I'm aware the rods being sold on www.fxr150.co.nz are competition rods and therefore that would mean a large portion of the bikes out there wouldn't qualify, especially in the South Island. I'm sure that JC's 125 twins (the fast ones anyway) aren't running stock rods etc.......

If it's OK to change the piston, surely it's OK to change the rod?

This will be an interesting discussion!!!!!!

I hadn't thought about the rods on that fxr150 site good point I'm putting a protest in now
we will ban them dam fxr's 1 way or another :Police:

na I dont realy care and i say it's an aftermarket part not a race part lol
it's a road bike after all not a race bike like the cbr150's
no one other than buckets race them

[TZ350]

I've only got one thing to say to that:

It's been a long time since I saw a 2 stroke win anything in F4..... I'm sure there is a lot of potential for it to happen but I haven't seen it for a long time. Rob was going really well at Taupo but still a long way behind Rick and Dave on their FXRs. If Rob could have held more corner speed he might have been in with a chance, I know I can't catch him on a straight section.


Its been a long time since a 4 stroke won a F4 GP so 4 stroke riders should cherish last Saturday, it might not happen again for a while.

The fact a Grey haired old man could threaten the cream of the 4 stroke world should give every one pause for thought. He has finished more races than most and headed Tim (FXR 150) the eventuall winner for most of the last race.

A quick look through the Mt Wellington results shows all 4 strokes in the top positions except for the GP's.

.

[bucketracer]

It's a mute point in the rules

"Engines must be derived from non-competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts are not permitted.

If it's OK to change the piston, surely it's OK to change the rod?

This will be an interesting discussion!!!!!!

Corect me if I am wrong, but a rod is an engine part right!!! and so special compition rods are excluded regardless who makes them. Re recent Boysen dual reed thread.

The FXR's look like they have a fatel flaw that will afflict all of them eventually.

The only Bucket legal (sprit of buckiting) way is to find a better rod from some other road bike or hand make them like Burt Munro did.

I recon I could hand make one if I needed too. :msn-wink:

Having Wiesco make a batch is a money arsed copout.

.

[Rick 52]

I would love to run a 2 stroke 'to me they are true race bikes but much harder to ride 'A GP in a RS frame is the way forward I think 'and I am saving up now .

[Kickaha]

I hadn't thought about the rods on that fxr150 site good point I'm putting a protest in now

Put in as many protests as you like, they are Suzuki genuine parts so it wont do you any good

[Buckets4Me]

The rod I got from them was a Suzuki rod, there's nothing special about them

had a look and they are genuine parts therefore legal

sounds like the other meltdowns where due to not building replacing the engines right not the rod being shoddy just old
or just maby the engine was over reved like crazy once or a dosen times


Wiseco pistons are ok but rods arn't as they are engine parts
pistons carbs being open as long as they arn't over the cc limit

[Sideways Sam]

Corect me if I am wrong, but a rod is an engine part right!!! and so special compition rods are excluded regardless who makes them. Re recent Boysen dual reed thread.

The FXR's look like they have a fatel flaw that will afflict all of them eventually.

The only Bucket legal (sprit of buckiting) way is to find a better rod from some other road bike or hand make them like Burt Munro did.

I recon I could hand make one if I needed too. :msn-wink:

Having Wiesco make a batch is a money arsed copout.

.
I reckon making one is a good option but there's a good chance that it would be possible to get a rod that fits out of another road bike. I'd trust something made in Japan a helluva lot more than something made in Thailand

Actually, I think the bikes are assembled in China by Lion Motor Company! If it's anything like Lion beer it'll all turn to crap overnight..........

The rod specs are as follows if anybody knows of something that might fit. Length can easily vary by a few mm as can the top end width, everything else needs to match though:

Big End Dia = 38mm
Little End dia = 16mm
distance between centres = 102.5mm
Width at Big End = 17mm
Width at Little End = 18mm

Pin Dimensions = 30 x 53???

Buggered if I know how to work out the big end bearing specs, haven't managed to get that far into my engine yet, need special tools.

[Buckets4Me]

Put in as many protests as you like, they are Suzuki genuine parts so it wont do you any good

All talk dont listen to me
just making waves pluss I was miss informed about them being special rods HAHAHA fool on me

[Buckets4Me]

I would love to run a 2 stroke 'to me they are true race bikes but much harder to ride 'A GP in a RS frame is the way forward I think 'and I am saving up now .

ride mine first they are SMALL!!!!!!!!!!!!!!!!!!!!!!!!!

take up Yoga first

[bucketracer]

I reckon making one is a good option but there's a good chance that it would be possible to get a rod that fits out of another road bike. I'd trust something made in Japan a helluva lot more than something made in Thailand

Actually, I think the bikes are assembled in China by Lion Motor Company! If it's anything like Lion beer it'll all turn to crap overnight..........



Right on, I hope something suitable can be found. I am looking forward to getting my TF100 out there and humiliating some of those FXR's if there are any left running by then.

Secretly my TF would like to be a FXR when it grows up.

[Sideways Sam]

had a look and they are genuine parts therefore legal

sounds like the other meltdowns where due to not building replacing the engines right not the rod being shoddy just old
or just maby the engine was over reved like crazy once or a dosen times


Wiseco pistons are ok but rods arn't as they are engine parts
pistons carbs being open as long as they arn't over the cc limit
Just cause it's made by Suzuki doesn't mean it's not a race part.... They have a whole division dedicated to manufacturing race parts.

If they're not standard FXR parts they are race parts (aren't they?). The way I've had it explained to me by some Mainlanders is that the parts they are buying are racing parts.........

The way I read the rules, as long as your engine is "derived" from a non-competition engine and you're not using competition parts in your transmission (I think that is referring mainly to clutches) then just about anything else is OK.....

I might ask MotorcyclingNZ to clarify the conrod thing. I know there are a helluva lot of buckets that don't have the standard rods in them. I'm rather keen to follow the rules, hence the all the mudguards and chainguards etc (and no kickstart) on my bike.

[Skunk]

If they're not standard FXR parts they are race parts (aren't they?).
The way I read the rules, as long as your engine is "derived" from a non-competition engine and you're not using competition parts in your transmission (I think that is referring mainly to clutches) then just about anything else is OK...
I might ask MotorcyclingNZ to clarify the conrod thing. I know there are a helluva lot of buckets that don't have the standard rods in them. I'm rather keen to follow the rules, hence the all the mudguards and chainguards etc (and no kickstart) on my bike.
I don't think MNZ would even know what you asking about - they wouldn't know a Bucket if they fell over one.

'Aftermarket' does not mean 'Racing'. Most Buckets have aftermarket parts as soon as they get rebuilt the first time.

The engines are derived from road-going bikes; that's all that really matters. If you're clever enough to fit an aftermarket rod from some other bike (R6 or some such) good on you.

[TZ350]

I know there are a helluva lot of buckets that don't have the standard rods in them.

It does not have to be a standard (original) rod but a rod derived from any road bike, I have been using RD400 rods because I have a number of them in my bucket of bits, unlike the original they have slotted big ends and can run silver plated RG big end bearings. They are also longer than the std, rod and with a thick cylinder spacer add usefully crankcase volume.

[TZ350]

I would love to run a 2 stroke 'to me they are true race bikes but much harder to ride 'A GP in a RS frame is the way forward I think 'and I am saving up now .

Bugger, if Rick gets one of those he will be impossible to catch. :weep: Hope he is just trying to frighten us.

[Sideways Sam]

I don't think MNZ would even know what you asking about - they wouldn't know a Bucket if they fell over one.

'Aftermarket' does not mean 'Racing'. Most Buckets have aftermarket parts as soon as they get rebuilt the first time.

The engines are derived from road-going bikes; that's all that really matters. If you're clever enough to fit an aftermarket rod from some other bike (R6 or some such) good on you.
I'm with you on that. I think the intention of the rule is that we aren't running CRF150R motorcross motors or similar......

The whole idea of a Formula is that you can modify the engines etc, that's half the fun of it...... I don't even ride the bike, I just make it go as fast as I can for my son (who seems to have no fear!)

[Bren_chch]

In my experience the rods seem strong, but the end bearings could be a weak point.

The FXR engine I built that won the BOB was bought as a dead engine which had been run out of oil... it had stuffed the cams and pretty much the complete top end, i rebuilt with, Longer duration cams, raised compression, ported head, flatslide carb, new CDI with better power delivery and no rev limiter, spanky header pipe and muffler... the bike was a ROCKET and i'd guess it was about 18 - 20hp and it went well for a while till it dropped the end beaings, not the rod but the end bearings... which was bound to happen eventually given the state i bought it in... i stuck in a new rod kit and it won the BOB and its never missed a beat since. it now gets some serious abuse from its new owner! :laugh:

This is the first time i have seen an actual broken rod!

Good work dangerous!!! :Punk:

If a rod has broken then something else has failed to cause this. Rods dont break like that on engines that are in the bucket hp range, generally something would have to have stopped the rod/piston from moving in whatever direction it was going.

I would like to know what sideways did to his topend that made his rod break i the time it did. can you share?

[Sideways Sam]

In my experience the rods seem strong, but the end bearings could be a weak point.

The FXR engine I built that won the BOB was bought as a dead engine which had been run out of oil... it had stuffed the cams and pretty much the complete top end, i rebuilt with, Longer duration cams, raised compression, ported head, flatslide carb, new CDI with better power delivery and no rev limiter, spanky header pipe and muffler... the bike was a ROCKET and i'd guess it was about 18 - 20hp and it went well for a while till it dropped the end beaings, not the rod but the end bearings... which was bound to happen eventually given the state i bought it in... i stuck in a new rod kit and it won the BOB and its never missed a beat since. it now gets some serious abuse from its new owner! :laugh:

This is the first time i have seen an actual broken rod!

Good work dangerous!!! :Punk:

If a rod has broken then something else has failed to cause this. Rods dont break like that on engines that are in the bucket hp range, generally something would have to have stopped the rod/piston from moving in whatever direction it was going.

I would like to know what sideways did to his topend that made his rod break i the time it did. can you share?
12.5:1 compression with the help of a different piston and 0.9mm squish
Standard Cams and Cam timing
Head flowed with 11% better flow
Standard Carb and airbox (rejetted)
Standard CDI (with rev limiter) etc
Running on race fuel
Will let you know the damage when I get her pulled down, that'll be after I get over the hangover from tomorrow night.....

Was running like a rocket ship, sounded like a Motard (maybe the extra compression?) The difference in bottom end torque was phenominal, if I'd had enough time to get the jetting right it would have been really impresive.....

[Bren_chch]

'cam timing' You slotted your sprockets? thats COOL! :D

[Sideways Sam]

'cam timing' You slotted your sprockets? thats COOL! :D
To tell you the truth, there's no option if you've adjusted the deck hight.....

The difference between teeth on the sprocket must equate to about 16 degrees of crank or more. After my deck milling job (to suit weird and wonderful piston) factory timing was half way between 2 teeth!

The timing is very cool though, you can tweak it for for different rev ranges..... Would be an interesting adjustment between different tracks....

Have you ever played with injection and management systems? That will be my next project, rather than replacing the carb.... Then there is even more adjustments to play with.....

[Buckets4Me]

cant wait to see what you turn up with next year now
Tim Richard Olly Karl Dave you guys had better watch out

[bucketracer]

To tell you the truth, there's no option if you've adjusted the deck hight.....

The difference between teeth on the sprocket must equate to about 16 degrees of crank or more. After my deck milling job (to suit weird and wonderful piston) factory timing was half way between 2 teeth!

The timing is very cool though, you can tweak it for for different rev ranges..... Would be an interesting adjustment between different tracks....

Have you ever played with injection and management systems? That will be my next project, rather than replacing the carb.... Then there is even more adjustments to play with.....


And I thought 4 strokers were becoming boring and pedestrian with all those same-as FXR's. This project is starting to go some where. A talented rider/developer who has a few clues, combo, this is very very interesting. Do keep us informed of progress.:mobile:

[nudemetalz]

I know this is going to be a "so what" question, but what Loncin ones were fast there?
I'm currently modding mine to try to keep at present.

[dangerous]

Where are the rods breaking, are they all doing it in the same place?
mine was at the bottom...

[Bren_chch]

looks like ur going on a picnic! lol

[Sideways Sam]

mine was at the bottom...
Damn, that's impressive. Who was it that said 4 strokes were boring????

I love blowing stuff up but that looks sort of expensive. I'll post a picture of mine when I get it to bits, that would require getting out of bed which I'm rather attached to at the moment.......

[TonyB]

Dangerous, as the piston was cracked in half at the gudgeon, are you sure it didn't seize or something? IE the bike seized, piston cracked, then the rod broke? Just a thought.

[pete376403]

mine was at the bottom...

Did you have to cut the piston in half to get the gudgeon pin out? That would indicate the pin had seized in the rod or piston. That could cause the rod to break. What provision do these motors have for pin oiling?

And shot peining (stress relief) is well worthwhile for rods. Kevin Cameron did this on the US kawasaki Superbikes to resolve rod beakage, until he was able to get titanium rods made (which may not be acceptable under your rules)

[Pumba]

That's because your's is standard.

Yea I know, put gas in it and away I go.

[speedpro]

mine was at the bottom...

I've broken a few 4-strokes, including turning one to shrapnell, and to me that looks like a typical piston failure happened. I've cracked Yoshimura and MTC pistons from the gudgeon pin up and across the crown. I always put the cause down as over revving. I've also sheared off the ring lands and ended up with a stack of washers - ring land ring land ring. Heaps of boost and resultant detonation was probable cause. Rods and bearings have never been a problem but I have never revved beyond calculated reasonable limits.

If you do the maths on the forces involved the horsepower being made adds so little extra force to the piston it really doesn't matter. Revs are the killer.

[Buckets4Me]

until he was able to get titanium rods made (which may not be acceptable under your rules)

they are if you make them :wari: but by the sounds of it it's the piston and rider at fault here
over reving the engine something most of us are at fault with
I know someone shifted wrong and bent some valves in his 100cc f5 bike at Taupo as well

[speedpro]

"Technically", making an engine part for a bucket is against the rules. The rules state that the engine parts must be from a non-competition motorcycle. It doesn't actually say you can make them though modifying parts is OK. Noone cares though so it doesn't matter.

[dangerous]

and to me that looks like a typical piston failure happened.
Yeah... at 1st I was thinking rod broke, but looking and thinking hard Im thinking the piston failed causing the rod to drop bashing a hole in the casing then snaping...
There is some odd marke on the piston were it broke almost like impurities in the casting.



Did you have to cut the piston in half to get the gudgeon pin out?
Na... the piston top was found at TDC the pin was on the crank... it was only the rings holding the 2 halfes to geather.

[dangerous]

... ok, been thinking and I DONT think the rod was the problem.

IMO I think the stinking new piston disintergrated, the crank pulled the rod and pin down draging it around the crank smashing it through the casing... the rod then broke and the rests history.

[Sideways Sam]

OK,

I had thought she might be fixable but now I think I can trash just about the whole lot........

Here we go:

* - Shrapnel found everywhere, carb, exhaust etc

* - First sign was when I removed the plug which had the end completely destroyed

* - Crankcase smashed to pieces, originally I thought it was just the hole throught where the rod penetrated just behind the barrel but it has destroyed just about everything including smashing a large chunk off the front of the case

* - Barrel destroyed including crack right up one side and skirt totally missing (I found most of the skirt in the exhaust pipe)

* - Head cavity completely munted including 3 missing valve heads etc

* - Almost nothing left of the piston, most of it seems to be floating around inside the crankcase

* - Crank is a bit of a mess so probably won't be any good either

My guess is that the piston and valves came into contact, I don't know whether this happened before the piston lost it's conection with the crank or if the broken rod was a result of the piston hitting the valves.

Interestingly the rod broke at the top, unlike the other's I've seen which have broken at the bottom. By breaking at the top it could go up and down inside the barrel ramming the piston into the valves/head repeatedly which has obviously happened in this case.

Still don't know which comes first, the chicken or the egg..........

Has anybody ever thought about whether the coolong is adequate on these things? anybody run a temp guage?????? If they were getting too hot that could explain all manner of problems. Running too lean could cause similar issues, I think that may have been my problem.

[stanko]

That will cheer up dangerous !

[Sideways Sam]

That will cheer up dangerous !
Yeah, he got off lightly

[Skunk]

I wonder if that's a piston failure too? A few bits get in the way and all hell breaks loose. Seems the engine wasn't stopped very quickly either (speaking from MY experience with GL145).

[Bren_chch]

fuk me thats impressive!!

I'd bet your piston split apart first... your rod then carried the gudgen and whatever was attached down and back up again smashing the shit out of your barrel, then pushing all the side wall of your barrel back up in to the remainder of the piston and then on in to the valves until the rod broke... i guess we will never know for sure.

[dangerous]

OK,

FARK................... :crybaby:

[Bren_chch]

What carb and what main jet did u run?

Apparantly The FXR's are meant to have better than average cooling for oil.

[Rick 52]

Shit mate that is wicked I have never seen one in that state.
I hope you find something soon and the right price .

[koba]

That is fucken amazing!
It looks as though the head has been dinged many, many times...

[Bren_chch]

Seems the engine wasn't stopped very quickly either (speaking from MY experience with GL145).

Keep it pinned skunk! lol

[TZ350]

A little demonstration of the kinetic energy stored in a crank that has a few rev's on.

[Buddha#81]

good effort........makes me want to leave my standard motor alone.

[speedpro]

The head damage suggests a valve, or a few, dropped before the piston stopped. The valves will eventually smash the piston which does not help the rest of the engine at all. I've seem a lot of engines with similar damage at various stages. Sometimes the piston is still more or less together and the head looks just like that.

Forged pistons anyone?? And what about a Carillo rod?? and "quality" aftermarket valves?

[dangerous]

The head damage suggests a valve, or a few, dropped before the piston stopped. The valves will eventually smash the piston which does not help the rest of the engine at all. I've seem a lot of engines with similar damage at various stages. Sometimes the piston is still more or less together and the head looks just like that.

Forged pistons anyone?? And what about a Carillo rod?? and "quality" aftermarket valves?

Yeah thats what I was thinking, same damage when my CB droped two valves.

forged, carillo... yeah right these engines are a malaisain run about only that spilled over to NZ, china parts only.

[Sideways Sam]

Yeah thats what I was thinking, same damage when my CB droped two valves.

forged, carillo... yeah right these engines are a malaisain run about only that spilled over to NZ, china parts only.
There is another option....... I didn't recheck the valve piston clearance after adjusting the valve timing which moved by about 8 degrees. Theoretically that could do it, allthough it's unlikely in my book.

I've never heard of an FXR dropping valves, all the retainers are still in place and there are no broken springs.... I was running the factory CDI so the rev limiter was still in operation which should eliminate valve bounce......

[TZ350]

Did you change the cams? Extra lift? With the changes to the head and barrel, could the valves have been getting caught on the outer edges of the valve pockets cut/cast into the piston crown? 8 degrees, could the valves have come together and hung up long enough for the piston to hit them?

[cmac]

OK,

I had thought she might be fixable but now I think I can trash just about the whole lot........

Here we go:

* - Shrapnel found everywhere, carb, exhaust etc

* - First sign was when I removed the plug which had the end completely destroyed

* - Crankcase smashed to pieces, originally I thought it was just the hole throught where the rod penetrated just behind the barrel but it has destroyed just about everything including smashing a large chunk off the front of the case

* - Barrel destroyed including crack right up one side and skirt totally missing (I found most of the skirt in the exhaust pipe)

* - Head cavity completely munted including 3 missing valve heads etc

* - Almost nothing left of the piston, most of it seems to be floating around inside the crankcase

* - Crank is a bit of a mess so probably won't be any good either

My guess is that the piston and valves came into contact, I don't know whether this happened before the piston lost it's conection with the crank or if the broken rod was a result of the piston hitting the valves.

Interestingly the rod broke at the top, unlike the other's I've seen which have broken at the bottom. By breaking at the top it could go up and down inside the barrel ramming the piston into the valves/head repeatedly which has obviously happened in this case.

Still don't know which comes first, the chicken or the egg..........

Has anybody ever thought about whether the coolong is adequate on these things? anybody run a temp guage?????? If they were getting too hot that could explain all manner of problems. Running too lean could cause similar issues, I think that may have been my problem.


I dropped a valve on a Triumph once (at about 80mph on a gravel road :eek5:) and the head looked just like this one. The difference was the piston didn't break - the valve ended up welded into the piston!
IMHO I reckon the piston/conrod have been intact with a loose valve head floating around the bore for quite a few revs - though I do acknowledge your comment about the stems/springs etc being intact.

[Sideways Sam]

Did you change the cams? Extra lift? With the changes to the head and barrel, could the valves have been getting caught on the outer edges of the valve pockets cut/cast into the piston crown? 8 degrees, could the valves have come together and hung up long enough for the piston to hit them?
Very possible...... Nice mess though, I'll bet your little model airplane engines aren't as much fun as this...........

Didn't change the cams at all, standard lift etc. In fact increased clearances a little bit to ensure valve/piston harmony

[Sideways Sam]

I dropped a valve on a Triumph once (at about 80mph on a gravel road :eek5:) and the head looked just like this one. The difference was the piston didn't break - the valve ended up welded into the piston!
IMHO I reckon the piston/conrod have been intact with a loose valve head floating around the bore for quite a few revs - though I do acknowledge your comment about the stems/springs etc being intact.
I haven't had much experience with dropped valves but if the retainer is still in place then surely the valve hadn't dropped? maybe the valve-head came off but I think a more likely scenario maybe the piston hit the valve and that caused the head to part company with the stem.......

Lot's of pondering but I should really just go out and buy a new engine!

[speedpro]

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.

[Kickaha]

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.

My experience with them (aftermarket) in the GN revving to 12500, was they lasted one and a bit meetings before destroying the engine

The factory Suzuki valves survived two years of getting hammered like that and were one piece

[Sideways Sam]

Two piece valves(cheap) are welded just behind the head. Stem is one material and the head is something different. Not uncommon when thrashed enmercilessly for them to part at the weld leaving the stem to go up and down and same for the head, just not at the same time or place.
Go figure....... you learn something new everyday.

I'm gonna have another look at them now!

Thanks for that

[Pumba]

Go figure....... you learn something new everyday.

I'm gonna have another look at them now!

Thanks for that

Them? Thought there was only one left:shutup:

[Sideways Sam]

Them? Thought there was only one left:shutup:
Yeah, you've got a point there :innocent:

[cmac]

I misspoke when I said the Triumph dropped a valve - it was the valve head that broke off.

[Buckets4Me]

time to look for a new engine
maby a 2 stroke can be found and fitted to you'r bike :msn-wink:

they never have a problem with valves dropping braking or coming into contact with the piston
but you can still make a mess with them

that is one nasty looking mess you call an ex fxr engine

hope you can find something soon to replace it with

[Sideways Sam]

time to look for a new engine
maby a 2 stroke can be found and fitted to you'r bike :msn-wink:

they never have a problem with valves dropping braking or coming into contact with the piston
but you can still make a mess with them

that is one nasty looking mess you call an ex fxr engine

hope you can find something soon to replace it with
I've managed to get another engine so we'll be mobile for the next Mt Wellington meet. Got a second one lined up for a spare. Each of them cost more than the whole bike did originally............ Ouch

Won't trust them till I've pulled them down and blueprinted ........

I just found out today that Ausies are buying FXR engines off NZ wreckers to race!!!!!!!!!! No wonder it's getting hard to find them at the right price.....

Might have to go 2-stroke!!!!!!!!!!! A GP125 in a FXR frame?????

Bloody Hell, might as well go to an auction and buy a bent SV650, it'd be a lot cheaper racing a Pro-Twin

[gav]

Maybe if the Aussies read this thread they may not be so keen! :Oops:

[dangerous]

That will cheer up dangerous !

errr... not quite, check out the remains of my bottom end :(

[speedpro]

that is very impressive, unless you own it of course.

[Sideways Sam]

Maybe if the Aussies read this thread they may not be so keen! :Oops:
Sheezus!!!!!!!! I want to open mine up now but I've just sold it to Brendan for parts...... Oh well, can't wait for the verdict.

[dangerous]

Sheezus!!!!!!!! I want to open mine up now but I've just sold it to Brendan for parts...... Oh well, can't wait for the verdict.

OHHHHH, the bastard, hes going to use your buggered engine to fix mine... christ its not going to have a chance a a decent life :doh:

[Sideways Sam]

OHHHHH, the bastard, hes going to use your buggered engine to fix mine... christ its not going to have a chance a a decent life :doh:
That engine came third in the Mt Welly 2 hour, there's nothing wrong with it (much).................:third:

[Bren_chch]

That engine came third in the Mt Welly 2 hour, there's nothing wrong with it (much).................:third:


SEE dangerous... u really got no excuses now!!! :clap:

[TZ350]

That engine came third in the Mt Welly 2 hour, there's nothing wrong with it (much).................:third:

One of the ESE GP125's came third the year before, then came first in a race at Taupo, did the 08 season at Mt Welly, this years 2 hour and the engine was then fitted to a new frame and did Taupo again without needing any maintenance let alone an engine overhaul. We at ESE feel for you guys peddling those delicate fragile 4 strokes....:bleh:..... sorry that was not called for was it...:rolleyes:..LOL..... P.S. running/complete secondhand GP engines can still be had for $100-$150.

[dangerous]

One of the ESE GP125's came third the year before, then came first in a race at Taupo, did the 08 season at Mt Welly, this years 2 hour and the engine was then fitted to a new frame and did Taupo again without needing any maintenance let alone an engine overhaul. We at ESE feel for you guys peddling those delicate fragile 4 strokes....:bleh:..... sorry that was not called for was it...:rolleyes:..LOL..... P.S. running secondhand GP engines can be had for $100-$150.

Ohhh man, i know what ya saying... I want me 33yr old stroker back :(

[gav]

P.S. running/complete secondhand GP engines can still be had for $100-$150.
Oh, so one of your S/H GP motors is only $100? :msn-wink:

[Skunk]

Oh, so one of your S/H GP motors is only $100? :msn-wink:
I'll be in for one too then!

[Buddha#81]

I'll be in for one too then!

Me to, I'll use it to run a fan to air cool my MotoFXR!:cold:

[bucketracer]

Me to, I'll use it to run a fan to air cool my MotoFXR!:cold:

Awww I duno, those ESE engines might just blow a lot of hot air. :jerry: