Rev's Wont Come Down

[copemech]

I think he has just being unlucky with the bike, as I thought right away dirty carb. However I washed the carb on a parts bath to really make sure it was clean and spotless. As the bike was still not running right. Air leak came to mind, but hey its sorted just hope the mains dont go

cheers copemech

Keeping the filter and box clean, and without washing in the dirt and grit seems to be the biggie here. I stand upon the washing precautions from experience, so be it!

Keep us posted ! And thanks for the feedback!

Cheers,

MC

[caseysherco]

I have a sherco 290 2004 model. the revs linger on that. how do i do the check to see if the crank seals have gone?

thanks

[shercojay]

Spray some carb cleaner around the flywheel and carb boot, if you see the cleaner been sucked in, its drawing the air in.

But before all this clean everthing

[caseysherco]

ok thanks will try that

[sherpat250]

new seals and its sorted, wasnt a bad job to do

cheers for the advice guys

ShercoJay,

Did you only replace the crank seals on the flywheel side, or the right side too? I ask because I am having a similar problem, yet replacing the seals behind the flywheel made no difference. I'm wondering if I need to do the right side as well?

[shercojay]

Hi, I did both sides just for peace of mind to be fair

[copemech]

It seems to me the symptoms on these deteriorating seals(due to alcohol induced fuel) may vary quite a bit!

Unexplained floaty idles(does not eliminate other problems), hunting and surging off idle, and the blowing out of tranny fluid(gearbox oil) could be symptoms.

As these seals must operate under rapidly changing events of both vacume and pressure generated by the 2T crankcase environment in which they operate, things may vary, and to add, there are two sides, one bathed in oil on the outside and the other, not! Vented purely by the crankcase vent tube, which could be blocked itself creating an unusual crankcase pressure(normally neutral).

As this is more of an operational and dynamic condition that may vary with the engine temps and such, and the seals plyability, there are several variables which may be hard to pin down. The exterior testing by detecting a noticeable fluxuation in revs by spraying a light aeromatic(carby cleaner) in or under the flyweight may be an excellent indicator, yet on the other side, unusual changes in vac/pressure on the vent hose is another. Some mitht produce bubbles when immersed in water after warm. Tey, (careful withthis) others may suck water up the tube(use clear hose).

I have not yet tested one using the short burst of the solvents up the vent to detect a change, yet as theory prevails at this point, it may well work as a detector!

Unfortunatly, I suspect we shall see more and more of this as time goes on. I estimate the lifespan of the standard(black) nitrile seals in this environment to be about 3-4 years. I do hope the factorys(Sherco and others) pick up on this and possibly make the change to the Viton seals which should be more resistant to the pump gas, yet that is to be seen.

In the big scheme of things, it is a minor issue, yet may cause major headaches in the fellows riding or fixing them. Add, it is not the factories fault we have s--t fuel!

[zippy]

Add, it is not the factories fault we have s--t fuel!

Is that why we call it "gas" here in the states????