LT80 Engine Damage Diagnosis
 

I dont know how to attach pictures to this post so if you could take the time to look at my profile page, I'll have a couple of pictures of the piston and cylinder in there. I rebuilt this motor a few months ago when I bought the quad and it has had maybe 3 full tanks of gas through it. I bored it over .040" and shaved the head .030". Removed the drive for the oil pump and switched to 1/32 premix. And for what it's worth pulled our 2 rollers out of the pulley. We took it easy for the first tank and then it was running great. It would out run our stock LT80 by 3 or 4 lengths in a 100 yard race. It did get a little bit cranky and start stalling when left to idle. And it seemed to run a bit better at the end with the choke on. It always smoked a bit though. More so than the other LT80 that we have. If you look at the pictures you can see how bad the fwd side of the piston is scored up on the skirt. It was a little worse than this before I rebuilt the motor. It seized up on us last weekend and I am not sure where I went wrong.

LT80 Engine Damage Diagnosis
 

Hrumph...Wiseco's do that. Unsure what happened.
What clearance ie: piston to skirt when bored?
What oil?
Exactly how much oil to a gallon did you use?

LT80 Engine Damage Diagnosis
 

Had sand make one of mine look like that. Intake boot to the carb developed a split & sucked in sand at the dunes. Probably not your cause but be sure everything is clean on the intake side when you put it back together.

LT80 Engine Damage Diagnosis
 

It was a suzuki piston. I am noy sure what clearance you mean? piston to cylinder? I took my new piston to a reputable local machine shop and the machined the cylinder to match. I did not check the clearance myself (piston/cyl.) though. I will have to admit that I use cheap oil but I use it in all of my quads and have for years. 4oz. per gallon. I did however switch it up to premium gas. What worries me is that this looks almost as bad as the one I just took out and it is the same kind of wear. I will check out the intake for any leaks.

In retrospect, I am almost positive that the edges on the ports in the cylinder were not chamfered. In fact, I just looked and they haven't been. Could that be the culprit? Is that something that I should have done before assembling or the machine shop prior to boring? The scoring is all in the skirt though and not on the sides of the piston. The rings are free and there are onlt two scratches that run above the rings. Would I be better off getting a new cylinder with a piston vs. machining to 1.5 over?