2 stoke crankcase seals?

[wtf?]

Gidday Guys, I do a bit of my own work on my bikes but have never split the cases on a 2 stroke.

Does anyone know whats up when (on say, an RGV) at idle you put your hand on 1 exhaust to block it at idle, the rpm drops and there is an audible release of pressure when you take it off, but do the same to the other pipe and there is none? In fact you can hold your hand there long as you want and it'll idle away quite happily. Where is the exhaust gas going? Is there a seal on the crank between the conrods that could be buggered?

Any ideas, thanks!

[bumsex]

yep there is. Would have to see the bike before you could say that the fault is definatly crank seals. Does the exhaust smell funny i.e not like two stroke oil burning?
what model nsr is your bike?

[F5 Dave]

Would expect that your pipe is leaking on that side. The engine will pump a heck of a lot more than could ever slip by a crank seal. If the seal on the RHS leaks, often gear oil will leak in & it wil smoke worse than crazy, if on the ignition side (LHS) there will be oil dribbling behind the flywheel.

So no it won't be the crank seal, but that's not to say that it isn't leaking. Presumably it is firing on that cylinder at low rpm. If not the pipe would stay cold while the other got hot from cold start.

[patch111]

Take the oil filler cap off while the engine is running and it will soon let you know if its crankcase seals. There should be heaps of blow by coming out of the filler hole. Also, a lot of times there will be a main bearing rumble that occurs with leaky crankcase seals, telling you its time for a rebuild.

Cheers
patch

[wtf?]

thanks lads for taking the time to reply. i now have an mc21 that is particularly smoky (blue smoke) when cold on the right (lower) cyl. the left (top) chuffs a bit at idle as if it is 4 stroking, if you see what i mean. no obvious oil leaks from either side of the motor. normal i guess. patch111- by oil filler cap, i assume you mean gearbox oil cap? After a hard ride there is no visible smoke at all at idle. Do you have any other clues as to when the main crank bearings are shot? thanks heaps

[wtf?]

also, i have just checked and there is no blow by out of the gearbox filler hole at all. the oil is about 3000km old and is clear, but looks to be holding in suspension some grey particulate matter. is that just clutch wear?

[Mr. Peanut]

Depends if its the dry clutch model or not. The oil pump seals have a habit of leaking into the gearbox oil, so it would be wise to check if that is the case.

[wtf?]

no, its just the r model without a dry clutch. does your comment still apply? im using motul 710 fully synth. what consumption is reasonable?

[Mr. Peanut]

Yeah, comment still applies. Not sure on my oil consumption, but it's fairly moderate. If you're churning through it, probably would pay to check it out. That said, I don't think its related to your problem.

[F5 Dave]

The lower cylinder is likely to get a bit of leakage from the carb run down into it & oil from the crankcase may dribble down into it so is likely to be the one to smoke a little when cold anyway. But if it were leaking it would likely smoke all the time, the spinning action bringing more through.

Not many strokers like idling for extended periods anyway.

[wtf?]

f5 dave, thanks. i too have been thinking along these lines. thnks for your thoughts