200x died after rebuild. Need diagnosis.

[michaelwbrenner]

Hey fellas. I'm a pretty good wrench but after you read this posting you may not think so. I was in glamis this weekend and my 200x died. This was the first trip on the bike since during this offseason I rebuilt the motor with a wiseco 10.25:1 piston 0.50mm oversize. I got the cylinder bored and honed and it looked great. I installed new valvestem seals, and lapped the valves. New spark plug, Carb is stock and freshly rebuilt/cleaned. adjusted the valves and adjusted the cam chain tensioner. New clutch, cleaned the air filter and filled it up with some fresh oil. Started on the second kick. Now. I check the oil again. Fired on the first kick. I'm excited now and it appears to run great! Has excellent throttle response and I haven't even timed the ignition yet. So. Here's the part I think got screwed up. I get my timing light and hook it up. I warm up the bike and let it idle. I set the timing on this 1985 200x to have the Circle marking on the flywheel that looks like "O" lined up at idle and check that it advances properly. I couldn't see any other markings on the flywheel and I figured that must be correct since it seemed to run and start easier than ever. Did i time it wrong???? When my girlfriend was riding the 200x she described some rattling and I'm think it detonated itself to death. I run pump premium (91 octane). I think it could have been underload and detonated itself to death. It stopped on her out in the dunes and I retrieved it later. The bike has zero compression now and turns over fine. What do you guys think? Also. What is the timing on a 1985 200x? is the mark "O" to represent full advance or is it base timing. I don't have the owners manual. thanks a lot.

[bonkers_200s]

no compression?

I can't say for sure, but that should have an oil pump yes??

I'm not sure because I have never personaly worked on one, but maybe your oil pump is shot, and you burned your rings?

[jeswinehart]

you are looking for "F" marking on the rotor if using a timing light.
when reassembing you will be aligning the "T" mark with the pointer affixed on the case ( under the cap on the right side of the motor ) and the "O" mark up on the timing chain sprocket to line up with the pointer at the top.

hopefully just a valve ( exhaust is my guese ) is hanging open.

i am used to doing valve adjustments after timing is set. it sure sounds like you had it dialed in right off the get go to me .

oil pump ???


john

[Dads]

Did you break it in before you went rideing the dunes???
could be broken rings. burned piston to lean. out of time bent valve.

[speed20]

predetonation would be a possiblity, but i see that more on 2 strokes than 4 strokes....sounds like a timing/valve adj. problem to me.

[michaelwbrenner]

Hey guys. I tore the motor apart last night. I'll post pics and you guys tell me what you think. The valves look ok. The piston and rings and cylinder look really crappy. I'll post pics in a few hours.