evo boy Posted March 21, 2015 Report Share Posted March 21, 2015 Hello all my mate need some help. He has a 2009 290 Sherco. When you start it up all it does is rev its self sky high. Throttle cable fine carbs been removed and clean including jets. We just don't know what's up with it. Hope someone has some ideas. Thanks Quote Link to comment Share on other sites More sharing options...
tony27 Posted March 21, 2015 Report Share Posted March 21, 2015 If the throttle slide is snapping back with an audible thunk then I'd be thinking ignition side crank seal or possibly leak at the manifold. Which carb is he running? Quote Link to comment Share on other sites More sharing options...
evo boy Posted March 21, 2015 Author Report Share Posted March 21, 2015 Thank you tony27. Its running a dellorto carb. How would you check the seal or a leak at the manifold? Thanks Quote Link to comment Share on other sites More sharing options...
copemech Posted March 22, 2015 Report Share Posted March 22, 2015 When did this problem start? Again-Can you hear and feel the throttle slide hitting the bottom stop when snapped closed? You gotta have a heluva air leak to do that much revving. Quote Link to comment Share on other sites More sharing options...
evo boy Posted March 22, 2015 Author Report Share Posted March 22, 2015 He's only just got it and seem to start the day after. You can hear the throttle hitting the bottom. How am I going to find this Air leak. Quote Link to comment Share on other sites More sharing options...
tony27 Posted March 23, 2015 Report Share Posted March 23, 2015 Spray soapy water around the carb etc while it's running & if the revs drop momentarily then you've found your leak Quote Link to comment Share on other sites More sharing options...
fitz2180 Posted March 29, 2015 Report Share Posted March 29, 2015 I just experienced they same issue. I put the bike away over the winter and treated the gas with stabil, as I always have. I started the bike last week and it didn't want to die without the choke. Common issue - I cleaned out the carb (no thanks to Stabil) and put things back together. Bam, first kick and she was purring. I took off the choke and the bike went from idle to high revs. I adjusted the idle screw and it eventually came down, but wanted to die. I adjusted the idle screw to bring the idle up a bit. It was idling well, then without warning began to rev like crazy! Also, if it is idling and you hit the throttle, it will stay up on revs for a very long time. Sound like an air leak somewhere? Thanks! 1 Quote Link to comment Share on other sites More sharing options...
robtrev79 Posted March 31, 2015 Report Share Posted March 31, 2015 Check the o ring on the top of the carb also if it's hard to start could be the base gasket but you should hear it chuffing if it's the base gasket Quote Link to comment Share on other sites More sharing options...
evo boy Posted April 6, 2015 Author Report Share Posted April 6, 2015 Hello Everyone. We finally got the the bottom of our Reving problem, after changing both crank shaft seals she is running a real treat. Thank you so much for all the help. Quote Link to comment Share on other sites More sharing options...
itstommmm Posted April 10, 2015 Report Share Posted April 10, 2015 I just experienced they same issue. I put the bike away over the winter and treated the gas with stabil, as I always have. I started the bike last week and it didn't want to die without the choke. Common issue - I cleaned out the carb (no thanks to Stabil) and put things back together. Bam, first kick and she was purring. I took off the choke and the bike went from idle to high revs. I adjusted the idle screw and it eventually came down, but wanted to die. I adjusted the idle screw to bring the idle up a bit. It was idling well, then without warning began to rev like crazy! Also, if it is idling and you hit the throttle, it will stay up on revs for a very long time. Sound like an air leak somewhere? Thanks! Same is happening on my beta Quote Link to comment Share on other sites More sharing options...
copemech Posted April 10, 2015 Report Share Posted April 10, 2015 Good call by Tony, and good feedback on the fix. Just another example of my 2-3 year theory on the stock seals, yet normally things do not get that bad overnight! Quote Link to comment Share on other sites More sharing options...
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