1994 CR250 L Crank Seal

[keithb7]

My engine has been surging, hunting, at idle since I bought it this spring. Mainly when the bike is hot. I played around with the pilot screw to no avail. I rebuilt the top end this spring as the last rebuild date was unknown. I just decided to live with the idle problem as it runs perfect other than at hot idle. It runs great, just revs up and down a little automatically. Well today my 14oz flywheel weight arrived so I decided to yank the left side apart while I was in there and replace the left crank seal, thinking maybe this is where the air leak might be. I was amazed to find over 1/2 of he thickness of the crank seal was out past where it should have been sitting. Like it was 1/2 to falling out. I was thinking the only thing keeping it from going further was the magneto backing plate that bolts over the seal.

Is this a known problem with the 1993 left crank seal? Any others had this same experience? Maybe it was just not installed properly. I am thinking that this might had lead to the hunting at idle. I live in an area where I can't ride it near my home so I never got the fully warm up the engine to test it. Next ride out I'll know for sure.

 

[dante]

I think that is just a problem allot of bikes just develope eventually... One thing I've heard is that a crank seal going bad could be due to a crank bearing going bad and having a little bit of "play" causing the seal to fail... It could be time for a bottom end rebuild, but you might get away with just replacing the seal... Most bikes this seal can be replaced with out splitting the cases...
Another thing I doubt that you can see the crank seal without taking off the magneto itself... The easy way to tell if the seal is gone is if there is any oil residue inside that mag cover... If their is you know oil is getting past that seal, if no oil, seal is still good...
If it is the righthand seal the breather hose will blow air instead of suck air... You can put the hose in water and see if their are bubbles... Check all the archives search "crank seals" and read everything, allot of good information on this site if you use it...

good luck

dante

 

[Rider 007]

I've got a '93 CR250 that I've had since '93.

Admittedly, it doesn't see a lot of action anymore but it has never, ever broken or missed a beat.

Real good stuff. :cool:

:ride:

 

[darringer]

The left side crank seal cannot be bottomed out in it's bore. There needs to be an opening for the oil passage that lubes the crank bearing. I believe the seal should be just about flush with the case, but no deeper.