Jump to content
Sign in to follow this  

1990 RM250 compression

Recommended Posts

So I had the rm out today. It was having trouble idling, but that could be a jetting issue (most likely). Well anyway, when I kicked the bike I noticed that it seems to take almost no effort to start the thing, then it idles like crap. I was thinking compression. Asked a buddy to kick it. He pushed the kickstart by hand and the engine turned. He said "this is waaaay to low compression." Took it back to the garage, threw it on the compression tester. 155 PSI?? I personally thought this was pretty good. At any rate, the bike seems to have good top end, though there is some engine work that needs done. Bottom line, does anyone think it is time for a new top end? I'm not sure when the top end was last rebuilt. BTW I use this bike for trail riding, no hard riding from me. Not sure about the previous owners though, or when they may have last changed the piston / ring.

Share this post


Link to post
Share on other sites

I have the same bike. I'd be happy with that. I Just completed the top end. Freshly nik'd cylinder and matched to a pro lite piston. My compression test was 151 psi. That's at 3300'

Share this post


Link to post
Share on other sites

Oh wow I thought that was way under normal compression. So any idea what could be causing the easy kick-start? I mean it is really easy to kick this bike. I definitely think I'm going to pull the carb and clean it out, maybe rejet if I can figure it out to try to fix that idle. I also need clutch plates and new fork seals so I have some work ahead of me!

Share this post


Link to post
Share on other sites

I am a bit stumped As far as why it is so easy to kick over. That being said mine turns over by hand too. As for the fork seals are they blown out? It could be just some dirt keeping them from sealing? Quite often this can be the case and can be cleaned and seal again in only a few min.

Share this post


Link to post
Share on other sites

Not sure whether the seals are blown or not, but oil is coming from the top of the forks as well so they need rebuilt in a bad way. I should have done some of these things when I bought the bike, but I was in a hurry to learn to ride and neglected the bike some. Now I want to make sure I take care of the bike like I should.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...