1987 XR100 help!

[toyvette81]

well i bought the bike and replaced the intake valve.( it was bent) fixed a few other things and the bike ran great... for 1 day lol, then it bent the exhaust valve... i am 100% that timing was correct but my best guess is the timing chain tensioner was not tight..( the bolt was "literally" tight on the outside, but the tensioner is lobe shaped so that in turn means the tensioner was loose..
the flywheel would spin by hand on the bike w/out turning over the motor... like the chain was slipping on the bottom gear.. many people told me that gear down there dosn't wear out and that wasn't it. but i know it was spinning around on that gear. but hopefully the chain just very loose. i can fix the bike in about an hour but the new valve is about to bend also,
what do you guys think

[sandpuppi101]

wow, that is weird that ,that happened! I got a 85 xr 100 awhile back with pretty much the same symptoms,0 compression ,bent valve and after talking to a buddy who works on bikes he told me the strangest thing ,that the sump which pushed the oil to the top of the motor was probably plugged and no oil was gettong to the cam or the chain up top.Well I checked and sure as sh** there was just a trickle of oil and that was it! It sounds like the same deal with you ,I have'nt went and got it running yet,been busy,but maybe that will help you out and let me know how it goes so maybe we can help eachother through these bikes!

[MTS]

who ever says the bottem gear doesnt wear out is FULL OF ****!, when you replce timming chain, you do BOTH gears.

[grundlegrabber]

Most common issue with those motors is the cam journal in the head wears out from lack of oil circulation. When this hapens, the cam goes down, and the tensioner can't take the slack out of the chain. And good luck finding a good head for a reasonable price. I have been looking for one for a year for a build up I was gonna do on an '85 XR80.