February 4, 201412 yr My 2011 st290 keeps revving quite high as if the throttle is sticking but im sure its not, I have noticed a little bit of oil or water (im not sure) coming from the base of barrel at the back towards the carb when I rev the bike? Any ideas what this could be? Does it seem to be common? I am hoping its the gasket or o-ring between engine & barrel but my mate seems to think there a machined part that just sit together??? Or could it be the crank case seals?
February 4, 201412 yr id start by checking everything is tight get the spanners out and go round everything
February 4, 201412 yr take the flywheel cover off and check the seal, air being sucked in can cause the high revving. Also check the carb to barrel boot for any cracking or leaks as this will also cause revs to rise
February 4, 201412 yr It doesnt matter if they are known to come loose, they can come loose. I would be surprised if there is not a gasket in the base joint, Just go over all the bolts, nuts etc and check them, dont force them too tight but if some thing turns easily, chances are thats where your problem is. It could be crank seals if your bike has had a hard life, but more likely I think that it is a joint somwhere. Check carb joint too. TLTEL
February 4, 201412 yr It would appear to be a blown base gasket mate. With case induction, as I imagine the Sherco's have, I would expect this would cause your high revving issues. High revving is usually caused be a lean mixture. It is something you need to address ASAP though as it may cause you bigger problems if you continue to ride it running lean.
February 5, 201412 yr If you are sure carb is slamming shut, it would normally require a fair leak to cause that type revving, as the seals just normally go to irregular and floaty. Shoot the area gently with some wd40 or carby spray to see if it picks up quickly.
February 5, 201412 yr Author thanks for replies the bikes now in the workshop having new carb to barrel block fitted, new base gaskets and new crank seals just incase.
February 20, 201412 yr hi, im having similar problems on my sherco 250 2011, did you resolve the matter?
February 21, 201412 yr It sounds like a lean running condition. If replacing those gaskets does not fix it, clean all the carb [passages very well and check the height of your float bowl.
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