86 RM250 issues

[Tony Two Times]

Hi all,

Got meself a VMXer after a long time standing on the outside looking in. Yeah yeah I know it's pre-90 but I'm in Qld and the likelihood of convincing a bloke to sell me his race ready 250N for the $2000 I paid for this one are pretty slim. So pre-90 I is for a little while.

Anyway the bike runs pretty good and is generally in good nick. It came out of the US and had a pod on the carby. I rode one meeting with it like that beforee finding and fitting an original air box and filter. I took it out for a practice run on the weekend and now there is a solid film of oil on the right hand side of the rear tire. The engine has no leaks so I'm scratching my head wondering where it's coming from.

Obvious guess is the exhaust. But why ?
Is it running way to rich because jetting was set for the pod ?
Has it sucked oil up from somewhere and blown it out the exhuast ?
The exhaust had a spark arrestor that I removed. Is it the crap that has been building up in there for who knows how many years ?
It's running fine but are the rings rooted ?

Anyway I do most of the spanner work on my bikes myelf but it's my first 2 stroke in many years so I'm on a steep learning curve.  Any advice would be appreciated.

T2X

[holeshot buddy]

11 hours and no answer thats a record

could be oil fuel mixture excessive oil amount
and gunging out exhaust
or maybe crank seal pumping oil out of gearbox
check gearbox oil level
or gearbox could be overfull and coming out breather
what ratio oil mix are you running
cheers rusty

[Tony Two Times]

Thanks Rusty. Figured the slow reply might have been because it's not a real VMXer 

I was on a similar track last night..........

Fuel is mixed at 33:1.
Dropped the gearbox oil. Motor says there should be 800ml in there. Looks about right when measured with the Mk 1 uncalibrated eyeball.

Figure I'll wash the bike, repack the exhaust, refill the gearbox oil and see if it happens again. If it does maybe I am looking at a crank seal.

A bit over a week to my 2nd VMX meeting. Gotta get it sorted !!

T2X

[Lozza]

Maybe the rear shock

[Tony Two Times]

You callin' me fat?

[Stan S]

A quick check of the conditon of your gearbox side crankseal is while it is idling gently unscrew the gearbox plug, normally if the seal is leaking when you remove the plug the engine will rev up as it sucks air in. Not fool proof but a pretty fair indication.

Stan

[All Things 414]

Or...... get a vacuum gauge like the cheap ones you get from Autobarn and hook it up to your gearbox breather hose (most pop straight on). If it's suckin' it'll show it on the vac gauge. 

[Tony Two Times]

Well I bit the bullett yesterday. Rang the Suzuki dealer. They said they could have a crank seal in for me today. Pulled it apart last night. All good so far.

Went to the dealer to pick up my bit today at the allocated time. No go. On a truck somewhere apparently.  Have to wait till next week.

Just once I'd like to be pleasaently surprised by a bike dealer and not disapointed.

T2X

[Hoony]

so did you diagnose the crank seal to be the issue or just decide to do it anyway? hope your putting in new seals both sides while your there ( and even consider a set of main bearings as well).

[vmx42]

…hope your putting in new seals both sides while your there ( and even consider a set of main bearings as well).

Come on Hoony, it's not a Honda!!!

[Hoony]

Come on Hoony, it's not a Honda!!!

My point Exactly Keeno, its a Zook, therefore better to ensure of reliability where possible 

[Billet YZ]

…hope your putting in new seals both sides while your there ( and even consider a set of main bearings as well).

Come on Hoony, it's not a Honda!!!

Yeah Hoony, what were you thinking. If it was a certain Honda you would need to throw a crank in it as well, just in case you know. 

[whitey 43]

While you have it apart, lock the evac system shut.They had a problem of bouncing open & shut over rough ground,giving a weird power feeling.From what ive been told,most riders did this with the '86.Apprantly the '82 model head fits and gives a way better powerband...
Thats what ive been told,hope it helps...

[evo550]

Did you try refitting the pod first and see if that changed anything?
Going from a pod to an airbox would certainly make a huge difference to your air/fuel mixture ie richer.

[Tony Two Times]

Good point. No I didn't. But I should have the crank seal today and fitted tonight. It would be a Homer moment if I fit the seal and still have the problem. But I read this and was pretty well sold on the diagnosis.........

http://dirtbikedoctor.com/page/2

T2X