What happened to my motor??

[Bmxr152]

Long story short i was doing a pull and blew some smoke, checked compression and had 80 on cyl 1 and 180 on the rest. Took the motor apart to find a few problems, one was the clutch springs and the second was the cylinders and pistons were scared. I was told it was piston slap but i never drive i hard cold. heres some pics

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Heres a picture of the piston i pulled out of the cylinder in the first pic. The others look alright. You cannot see it in the picture but the piston has some crack on the ring lands. So what do you guys think caused the piston to score the cylinder and only cause damage to one piston? also the main bearing closest to the tranny and the cylinder that was damaged had some scoring on the bearing?

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[ramsack]

the cracked ring lands are probably what did it. cylinder #1 gets the least amount of fuel, as well, in most cases, so it's a recipe for knock.

 

[red1993gsallmt]

was the motor ever overheated? what kind of pistons are they?

 

[Bmxr152]

It did get overheated once, but that was like a month or so prior, and they are OEM 6 bolt pistons.

 

[Bmxr152]

could this have been caused by cylinder wash down due to a bad tune with my new 680cc pte's? Btw the cylinders still have nice cross hatching on them?? maybe a newer motor.

 

[feardafish]

Your water jackets on that side of that cylinder are clear of debris and not visibly clogged right? it almost looks as if the heat was in a concentrated area there. Something similar to this happened to my dirtbike when i first got it...turns out the guy before me put the head gasket on wrong and covered one of the water jackets on half the motor .

 

[viprez586]

That cylinder (first pic) looks like it wore out causing piston slap or piston rock - which is why the skirt is all fudged on that piston.
Either way it's time for a rebuild.

 

[Bmxr152]

yeah im in the process of the rebuild, i just wanted to clarify, for future refrence. It blew at a WOT run at only 21psi. hmm must have been the chep rebuild done by the previous owner or something?

 

[viprez586]

Hmm, possible. Could have been a lot of things - including the tune.

 

[ziggo0]

Piston to wall clearance will also play a roll in that. If it was to tight the skirts rub the cylinder wall smooth.

 

[JacksonAuto]

Looks like lack of oil and/or insufficient PTW clearance. I also see spots on the cylinder walls with more wear than others. That tells me the cylinders weren't round.

 

[Bmxr152]

Thanks for the input, its always nice to hear from the Pro's!!This was supposed to have a newer motor, everything i took out was OEM on the engine internals though. It did get hot enough a couple times to throw the CEL at 234*. Well im betting the block bored and honed .020 over so hopefully it will be good this time.

 

[JacksonAuto]

Shoot me a PM if we can be of service.