Yamaha 800 PV with scorched piston

[meatball]

Im currently working on a Yami XLT 800 that either needs a whole new motor, or just a cylinder. The front piston is scorched on the intake side, apparently from the P/O not torquing down the cylinder correctly (Is this plausible?). My question is, is the bottom end still good?

I checked for grinding sounds and heard none, there is no rust anywhere and there is no up and down play on the rods. What else can I check? Also is there any reason the bottom end would be bad from just a scorched piston due to the cylinder not being tight?

And is there any chance there might be metal down there? It's just scratches, so I wasnt really thinking there was metal in there but might as well ask.

While Im at it, what type of top end failures constitute a new bottom end? Ring failures? Scorched pistons? Piston failures? Wrist pin failures?

This motor was rebuilt before the piston failure so Im not worried about age.

 

[vomitspot]

i have a good piston /cylinder pm me if interested
jason

 

[meatball]

I took another look at the cylinder and found a chunk of metal missing which is uncommon for these nicasil plated cylinders. Because it might of possibly found its way into the bottom end, Ill probably just replace the entire motor. Besides, unless you're cheaper then a bore/hone/re-plate and new piston from SBT I'd rather do that.

 

[Boris]

I have a few of those cylinders with chunks missing.
Just because it's plated doesn't mean that they don't coma apart once you snag the exhaust port.

 

[meatball]

Heres some pics of the cylinder damage. What do you guys think? New bottom end required? Im at the point where Im just gonna do a whole new motor.

The exhaust port gouge is about 1/32 of an inch deep. And the intake port gouge is about less then a 1/16 of an inch deep.

-Kevin

 

[Boris]

A new motor for that ????


Go on Greenhulk and pick up a cylinder and piston set. Slap it together and ride.
or
Bore and replate with a new piston.

 

[Boris]

i have a good piston /cylinder pm me if interested
jason

there's your answer.

 

[WaveDemon]

you should get jasons used piston and cylinder.

I've got a used set on the shelf too in case I end up in your situation.

 

[meatball]

It's not my ski though so I dont want to take any chances that there may be metal in the bottom end and have it blow up again. If it was my motor, then yea I'd do it, but I cant take any chances here.

-Kevin

 

[Boris]

What metal ?
The shavings have you worried ?

That thing just had a little clearance issue between the piston and cylinder. It's not like you had chunks breaking off.

Here's what my last piston looked like.
Nothing major.

 

[WaveDemon]

It's not my ski though so I dont want to take any chances that there may be metal in the bottom end and have it blow up again. If it was my motor, then yea I'd do it, but I cant take any chances here.

-Kevin

then take the case apart, clean and inspect the crank. There's no reason to throw good money away.

 

[Idok]

It's not my ski though so I dont want to take any chances that there may be metal in the bottom end and have it blow up again. If it was my motor, then yea I'd do it, but I cant take any chances here.

-Kevin

this is where you call your customer/friend and explain the options........

then take the case apart, clean and inspect the crank. There's no reason to throw good money away.

for real! especially these days! (I hate saying that)

 

[JetManiac]

I have a cylinder that was resleeved but never used.

 

[meatball]

this is where you call your customer/friend and explain the options........





for real! especially these days! (I hate saying that)

I did explain it to them, and they choose a new motor. I told them there was a small chance the bottom end could go again, and that was all she wrote. No saving money here...

-Kevin

 

[Idok]

then I'd shop around for REAL core parts...keep those and make a little extra $$$