Hi all

Iv got my 290 2006 sherco out of the garage where it's been for the last 18 months.

Put in new fuel, cleaned carb, new plug, cleaned air filter/box etc..

It started straight away to my surprise, BUT!

It's over revving, not just a little but at full revs, and won't cut out. I'm really worried that if I try again the engine will blow up. The only way I could stop was shutting off the fuel.(was going to stick in gear with breaks on but not ridden for a while and clutch sticks a bit, so didn't fancy getting splatted against wall!)

Idle screw on carb is as it was before I cleaned, 3 1/2 turns. Throttle cable seems ok, I can see everything sliding up and down as it should within carb when air box is off.

Something is defiantly stuck open but I don't know what???!!!!

Any help would be great!

Thanks

Confirm that cable is operating. Do not pull H/T lead off to stop bike. Check for air leak on intake rubber, this is a frequent issue with Shercos.(maybe others as well?) As previously suggested, blocking exhaust outlet is easiest way to stifle revs while trying to locate problem. 

Hi rich

The throttle seems to function as normal, and springs shut as it should.

Thanks for the tips, I'll feel much more comfortable when I try and start it nxt time!

Hi big bob

I'll check the rubber connections for leaks!

See the top of the Beta forum for a clutch fix. I think it should work for the Sherco as I believe they buy their clutch plates from the same supplier. Thus the same sticking problem.

All the suggestions for checking air leaks are good. Taking the cable out of the throttle housing and making sure it snaps back with a loud thwock from the carb body. There is the obvious chech of the idle screw.

I'm not sure WD40 is useful for leak detection anymore. I'd heard they stopped using propane as a propellant though I could be wrong. Starter fluid will work. Spray in short bursts and let dissipate between. You don't want to be in a big cloud of ether when you are taunting a sparking machine.

Oh yeah second the "Don't pull the HT lead" comment. Did that once. Never again. I'll let a motor blow itself to smithereens before I try that maneuver again.

also check carb top is tight

Thanks all, great help!

Turns out that although the throttle seemed to be shutting off and opening, it wasn't fully closing, I disconnect cable from the housing on handle bars which allowed it the slack to close. Started, much better but still over revving so got a damp cloth to put over exhaust which allowed me the revs to make a few minor adjustments to the idle screw. All running like a dream!

Thanks all, proper group effort!!