Hi to all!

I was just wondering if anyone can help me on this matter. I have an 04 250 sherco and i was out practicing the other day and as you do i decided to give it it a quick blast on the throttle to clean it out. After this I have lost all bottom end power and it doesn't want to tick over or run properly. What could this be? It fires every other stroke with quite a bit of smoke. Not sure if you can knock the timing out or whether i've broken something internally. Please could someone help!!!!

Cheers!

Try pulling the flywheel to see if it has sheared the keyway!

cheers for the advice guys. I guess the symptoms I suggested woud lead to the snapped key. As for the broken piston ring how do I check for this would i have to do a compression test. How expensive is it to sort this problem out?

Steve,

Could be a crank seal on the clutch side of the crank, will cause lots of smoke with poor bottom end.

As far as checking goes for these probable problems how do I check for the crank seal or is it just a simple case of taking it all apart

Howard has seen some strange stuff and it is possible. I think in that case, if you drain the gearbox oil and measure it, it would be noticably low as the motor is consuming it!

Should pretty much be 450ml in, 450ml out!

I would also normally think that if the crankshaft seals are out on that new a bike, the main bearings are out as well causing excessive movement that the seals cannot seal. So check the flywheel side as an indicator as well.

Try moving the flywheel up/ down and left/right, there should be little to no play. I do not know of an official spec on this, but the bearings start out at .003 in clearance as I recall, add probably another .003-.005 in max allowable wear and figure the arm length to the end of the flywheel, so add .003 more as a general guide. You would have to pull the clutch side cover to confifm on the other side if found suspect.

Usually only excessive dirt and water entry into the motor(air filter) accounts for this type of excessive wear.