KX500 lost compression - help...

[DHregdovic]

Hey guys... Just thought I'd try to get a few opinions bedore I started tearing into it. I bought my '91 KX500 off a buddy that had it rebuilt by a shop appx 2 years ago but there has only been maybe 15 hours on the bike since then. It was running great until my front tire went into a large hole and I realized the handlebar clamps weren't tight enough. The bars went forward. I'm doubt that has anything to do with it but as I went to start it I had troubles getting it going (I normally start it just fine).

After I got it home I haven't been able to start it since - there is very little compression to it. I did get it bump started once and it seemed it ran ok but I only ran it for a minute so it may be low on power - I didn't want to run it long and create more problems.

Anyone have any suggestions? My main thought was I need to see hwat happened to the top end but I was wondering if it could be the KIPS being plugged up but not sure if that would affect starting comprerssion. I also had someone suggest that maybe it could be a kickstarter issue but it seems like it is kicking ok and I can feel a the compression when the piston comes up but I can also push it with my hand so we all know there is a compression issue. Thanx in advance!!!

[tharden]

Sounds like you have a scored cylinder.  I would pull the exhaust and the intake and figure out which side is damaged.  A pluged exhaust will not cause a loss of compression, but will make an engine run like crap. 

[DHregdovic]

I was figuring it was something like that. It's been down for a few weeks and I've been working like crazy. I hated to tear it apart and not have the time to put it back together - makes for a lost part or two when you have kids running around. Not to mention I also have a DRZ400 so it hasn't kept me from riding.