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broken piston

3K views 36 replies 13 participants last post by  Climb 
#1 ·
well i pulled the cylinder off for a lil work and i noticed this....wtf....what did this???? my pipe leaks a bit at the cylinder, could that have caused this? and where and y did a chunk come out of the side of the piston??
 
#2 ·
maaan!!! that frickin thing is nasty!!!

i would def say something is out of wack with your bore or the ex. port..or something got in there and tore it up..are there any similiar wear marks on the other side of the ex. port?...why the chunk came out like that i couldnt say..maybe it just busted from the crack that runs into it..or something hit at the chunk and that cracked it the rest of the way.i would check the bore for roundness!

i have several pipes leak..some worse than others and never had aproblem like that..i highly doubt a leaky pipe would do anything to that extent.
 
#3 ·
Mabey this is the cause why you said you lost or didn't have full power at the dunes dude.

What the hells the rust from man, you were running that shit like that YIKES!!!

Damn nasty scars on the poor piston....how the jug look?

Get-r-fixed.
 
#9 ·
if you can some good pics of the bore that be cool..or you already hone it?

i would say the cylinder got hot and swelled causing the hotter ex. side to expand more and jack the piston...

or like stated above the bore is outta round...the ones ive seen with and outta round bore usually break the skirts off though..that is an interesting wear mark...

is this jug ported?
 
#10 · (Edited)
ya ported, going in for some more work is y i pulled it. ports are good. i havent honed it yet, i am gonna do some work on the cylinder. i will take some more pics...looks like i got some contaminants in there...ya i am sure it got hot i ran the piss out of it at the dunes...or do u think it could be from not warming it up? if the cylider was outta round it would make certian spots wear faster but there are lots of fine scratchs in it..
 
#11 ·
not warming it up is not good..can lead to cold siezes easily..that could have done it..they can cold sieze,sometimes still run and mess shit up..60 hours isnt a real long time but i would still get a bore gauge and mic it thoroughly...
 
#13 ·
i would say you got side play from possibly a worn wrist pin bearings or excessive clearance on the bore ... once you get piston slap with all that movment you get blowby... hence the remnants of dark burned premix collected on the walls(not rust) ,in theory that service time isnt typicaly considered very long , but personaly i wouldnt wait that long to put in a new topend if i was running it hard .what kind of premix you running and was the bore checked yet ?



 
#14 ·
WRIST pin was purchased when i installed crank and wrist pin bearing. i and leaniNg toward warpED CYLINDER. dont know how , i was just bored when i put this piston in....and usually u can hear the piston slapping/rocking. i am gonna break out the mic when i get home. what should the piston / cylinder be?
 
#22 ·
to me it looks like the cylinder to piston clearence is not right plus it needs bored square.. if the exhaust port is to wide it is opening the transfers causeing blow by... / short circiut.. it might help to move the sqish band wider in front to aim the heat towards the back which is cooler .. from intake charge.. if there is verticle lines in from and back that is cold score..depending on how it was ported may allow the piston to rock.. imo
 
#26 ·
Ouch. Last piston I saw like that was deffinately an egged cylinder. You could here it slap just off idle and that's where the damage was happening. Time for some more work man.
 
#28 ·
Hmmmm weird. Not sure then. The Yamazuki is a world of mystery.
 
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