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Thread: Piston/barrel dramas

  1. #61
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    Click image for larger version. 

Name:	Piston side A1.JPG 
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ID:	247139 Mr Jellys blown Vincent piston.

    Quote Originally Posted by SS90 View Post
    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...
    Quote Originally Posted by bucketracer View Post
    PDF Attachment 246996

    picture 1.1.2 in the PDF,
    There you have it ... and I see it says "Damage caused by circlip"

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    Quote Originally Posted by SS90 View Post
    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.

    Quote Originally Posted by bucketracer View Post

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

  3. #63
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    progress!

    aye?
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    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 hasn´t even been wiped off the side of the crown above the first compression ring.
    I love the smell of twin V16's in the morning..

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    Quote Originally Posted by TZ350 View Post
    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.

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    Quote Originally Posted by SS90 View Post
    . ..
    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.
    Don't you look at my accountant.
    He's the only one I've got.

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    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?
    "Your talent determines what you can do. Your motivation determines how much you are willing to do. Your attitude determines how well you do it."
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  8. #68
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    Quote Originally Posted by SS90 View Post
    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.

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    Quote Originally Posted by Crasherfromwayback View Post
    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/Tro...s/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......

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    Thumbs up

    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


    Quote Originally Posted by jellywrestler View Post
    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?

  11. #71
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    Quote Originally Posted by SS90 View Post
    Well (your majesty), may I direct you to the very page that these guys refer to

    http://www.mlcmotorfactors.co.uk/Tro...s/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. Would expect more definitive marks if it lodged in there.
    "A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal

  12. #72
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    Quote Originally Posted by SS90 View Post
    Well (your majesty), may I direct you to the very page that these guys refer to

    http://www.mlcmotorfactors.co.uk/Tro...s/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.

  13. #73
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    Quote Originally Posted by Crasherfromwayback View Post

    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...........

  14. #74
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    Quote Originally Posted by SS90 View Post
    Those that live in glass houses...........
    Should wear clothes?

  15. #75
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    Quote Originally Posted by SS90 View Post
    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/Tro...s/PistonTT.pdf

    Page 10 to be correct.
    No, .... a fretted imprint maybe and a very good example of what Bucket has been talking about.

    Click image for larger version. 

Name:	Piston Damage.GIF 
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ID:	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.

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