Need Help with top end problems

[bone705]

ok here the deal. about 3 months ago my crank went out on my r. The piston was all chewed up on the top but we just figured it was from hitting stuff from the crank bearings. I put it back together with a spacer plate and an 86 style piston. Its been running great for awhile now and today after our ride i pulled into the driveway and it died. i tried starting it and no go. it had no compression. we pulled the top end off and the piston looked the same way the old one i replaced. i was hoping somone had an idea what was causing this problem. It ran fine all up till it happend. heres some pics.

http://www.imagestation.com/picture/sraid120/p00a1ca3444128ea1c3acb9a6c1dde8a3/f8635e69.jpg

http://www.imagestation.com/picture/sraid120/p890e16be717459d4466fde7940f6ce0f/f8635e61.jpg

http://www.imagestation.com/picture/sraid120/p7b9e9f2dad67575e48e09af86ec538c3/f8635e6f.jpg

http://www.imagestation.com/picture/sraid120/p6a19239b33fac35f7e14734c15dc36d4/f8635e5c.jpg

[bone705]

anyone?

[starky]

it looks to me as if you had some loose particules in your motor, ring spun, or maybe even detonation due to bad gas or even you might need to run race gas, what did your motor read when you had good compression?

[bone705]

i never did a compression test.

[nakomis0]

Only time I seen a piston like that is , just like you said, when the crank bearings went out and metal pieces get up there and just bounce around, and slam into the piston and head.

[s-10s_rule]

You need to break down and buy a new piston and rings and at least have the cylinder honed. For a few extra bucks you can bore it the next size over and replace all the gaskets. If you do that you will have no reason to have low compression and your piston is shot anyway. Thats what I would do.:D

[bone705]

honeing is out of the question. if i bored it id be lucky if .120 over took it out.

[RissExtremeATV]

U need to just sell the whole quad and go new school and get a 4 stroke. O and Clints swinger is in.

[RissExtremeATV]

o yea looks to me as if the circlip came loose and fell out and done all of ur damage.

[powerslider]

Something's failing again in the bottom end, the scrap is blowing up thru the transfer ports hence the scoring at the port roof and the piston. Take this motor completely apart......

[s-10s_rule]

Wow, I didnt read your initial post close enough, sorry for making all of you waste some time on reading that last post of mine and consequintly this one also:( looks like a wristpin clip to me also, well were both of them in there when you took the motor down?

[chucked]

dude that piston is trashed! ive seen ones in better shape be replaced