GPX250 oil leak

[Tack]

On sunday while out on a ride, I got a big oil leak on my 91 GPX250.

I got it home, pulled the fairing off, cleaned all the oil and road grime off, took the chain covers off and then started the bike up.

I noticed that the front chain sprocket looked a bit wobbly (it appears to be a loose fit anyway with just a circlip type retainer on the output shaft).

I noticed the oil leak coming from behind the front chain sprocket so i removed the sprocket and found that the output shaft seal was pissin oil out. I then spun the shaft and the bearing sounds noisy plus there is a fair amount of movement vertically and horizontally in the shaft (I haven't measured it and there doesn't appear to be a measurement for this in the workshop manual). I'm thinking that the output (thats what its called in the manual) bearing is stuffed and is allowing too much runout in the shaft which then stuffed the seal. However having had no experience with motorbikes (but 20 years of working on car engines, gearboxes, diffs and suspension) I'm unsure if the output shaft movement is normal or if the bearing noise is normal (they apparently have a very noisy gearbox). If it does prove to be normal I reckon that its a pretty poor gearbox.... . I don't want to just change the seal for it to just leak again.

My question is: Does anyone know if this a normal problem/known problem for this bike?

Has anyone had this fixed on their bikes before?

[Steve_TLS]

I doubt there should be any play in the output (counter) shaft at all. The bearing is probably shot causing the play and caused the oil leak like you said.

(It might be normal for a GPX but I doubt it ).

[ty]

I don't think it's normal (or 'expected') and there shouldn't be any play.
I had no problems like than on my clapped out old '89 GPX
ty

[Tack]

I ordered a new seal and then pulled out the old seal to replace it and.........the bearings is rooted...off its face.....missing balls...bits of metal everywhere.....so now its pull the engine out time and fix it.....this is gunna be fun!

[icebreaker]

it's all that clutchy mono's mate

[mike-s]

repeat after me:
"Thou shall not use a socket wrench and a hammer".

In all seriousness you were lucky that you found it before the shreds of metal locked the gearbox up on you. I just hope that the rebuild process is smooth and nothing else on the inside is damaged by this.

[bonester]

I betcha someone used a rattle gun previously to remove the front sprocket nut when replacing the front sprocket- quite common I have heard to cause this kind of problem.

[MickLC]

Yeah? How would a rattle gun cause that sort of damage? I would have thought someone swinging off a big wrench and hitting it with a big hammer would be more likely.