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Post Info TOPIC: strange piston damage help


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strange piston damage help
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i think my small end bearing  disintergrated on the way home i was takin it easy on the  new rebore an everything 

so i need one of them now too

 my piston   well  the damage thats gone on is wierd  ill whack up a pic if anybody has any advice on what went wrong id appreciate it

 

 

 



 
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it hasnt ripped up the piston walls at all .its like a meteor  hit the top off the crown

im not sure wether i damged the small end bearing removing it or thats what craterd my crown



-- Edited by tripr on Wednesday 4th of January 2012 12:36:32 AM



-- Edited by tripr on Wednesday 4th of January 2012 12:39:40 AM

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DTR Trusted Engine Builder

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yeah looks like some things been floating about in there is the head damaged also?

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My piston almost looked like that but worse after a long hard drive with a passanger and too small jet.

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Sold the DT, Bought a WR 426. Sorry guys.



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not really m8 its seems ok still theres few little scars there,nothing like the piston its got a 240 jet on a standard carb, but yeah your right it does look like iv been running it a bit lean by the look of the crown. luckily i hav'nt ridden it hard or for long at all since the rebore.

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Okay, weird



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Sold the DT, Bought a WR 426. Sorry guys.



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What spark plug do u use ?

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Sold the DT, Bought a WR 426. Sorry guys.



DTR Trusted Engine Builder

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piston metation ha

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just been using the standard iridium ones br8iex

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DTR Trusted Engine Builder

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did the previous piston break up b4 u put this one in ? looks like somets been floating round in the chamber with all the dints in the crown, did the little end break up or maybe some foren debri in the cases on the rebuild,
mi mate rebuilt his engine with out checking the crank cases and needless to say it went ding ding ding rattle clunk the dime bar ha ha

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does dont it the little ends in bits yeah. just dont know if it was destroyed when running or when i removed it , been an got a new one this mornin to try an get to my mrs house to slap on my other working top end on . but is sounding rough as nuts so i aint gonna risk the ride
i did have a piston break up a while back but i cleaned out the lower crank completly and i was runnin my other top end for a small while well the rebore was being done, there was no damage to that one

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DTR Trusted Engine Builder

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only thing is it only takes small amounts of material to get stuck in the bearings and lips of the seals in a crank case's on 2 strokes and soon as the engine run's it gets flushed round the engine and with the revs 2 strokes do it don't take long to destroy a new top end, when ever there's a catastrophic failure with debris in the bottom end id completely strip the bottom end clean /flush out with new bearings/seals piston kit/re-bore & little end for the sake of about £75 for the piece of mind it would give after its built

engines still going to be doing some decent rpms when the break up happens so bits will get every where in the engine any way

one good point is the steel bore on dtr's, instead of nikasil plating like most others engines,yeah it may last a bit longer but is way over priced for re-plating

hope u get sorted soon any way
norfe



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weak mix by the look of it to me.. check for any air leaks in the inlet manifild areas too(important). Upjet a size or two, which carb u running? 210 jet or the 240? mikuni?

if the bore is fine, then renew the piston and little end.. check crank for play.


use a normal plug on rebuilds, plug chop, plug chop plug chop. gives u a better indicator for fueling.

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if it was the plug the damage would be in the center,whats the head like?, or somebodys not been running there 99 Octaneno, whats the barrel like?

and what piston is it?



-- Edited by the only way is YAMAHA DTR on Wednesday 4th of January 2012 07:25:57 PM

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the heads off now its nailed the outer rim of it like debrit craters . luckily the barrels perfectly sound, was a new rebore sized to a mitaka 1.50 piston. where do you get 99% octane fuel then or is it somekind off additive

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When you had your over bore done did you also have the head done, the head gasket bored out, and the powervalve ground down?

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i thought it looked a bit lean to m8 iv adjusted that now was on third notch down on the carb needle its a 240 flatside  im runnin  sat  m8     strange thing is  iv changed it out for a fresh top end but  both my cylinders are now 1.50 over exactly the same an the one i was using  for ages on this setup  doesnt have a fault  

i have all my parts in hand now anyway lads im onit   after me chicken wings an chips av bin lol



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no m8 i did ask him about   when i had it done boring out the xtra 1.50 in my head an he looked at me as if i was stupid

the p/v ok tho cos  iv dealt ith that 1  myself before



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Reckon thats your problem then, tell laddo to ring up Cornish motorcycles in Plymouth up, they'll confirm you need to do all that, mine was bored out to 2.4mm oversize with a tzr 2mm oversize piston, they ground the head out, for cylinder volume, the head gasket too, because it would have a lip if it wasn't, and ground down my powervalve to suit

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feel like a right div asking this but do you think if there was bits in the exhaust , they could off gotten sucked back up into the piston chamber  causing it

iv found bits in there   ,,, got em all out  sanded the crap outta the piston to so it aint hitting nothing again  an got it running this morning.  but its still rough as a mother.

so in about 5 mins its coming back indoors  to coe apart an have the trusted run in top end refitted  till i get yet another +1.50 piston for this one before i damage a perfecly good rebore



-- Edited by tripr on Thursday 5th of January 2012 08:30:00 PM

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DTR Trusted Engine Builder

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yes thats possible pressure waves surge in and out of the exh port when running so could easily suck pieces in

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