November 8, 201114 yr Hey guys! I have a problem with my Sherco 2010 that is really bugging me... When cold it runs fine, when warm, on throttle slightly open throttle it tends to like rocking, or jumping forward. In gear or neutral. Found a guy a video on youtube with a similiar problem, but on idle. But his problem was a sparkplug related. I have a new spark plug. cleaned out carb several times. Changed needle position and both idle jet, and main jet to lots of combinations. Running 98 octane with 2% synthetic oil. Works fine on family members gasgas:es. cleaned fuelpump and hoses transporting gasoline. Changing jets help slighty, but does not eliminate it... What could it be?
November 8, 201114 yr Have you checked thoroughly for air leaks [i'm thinking around the reed block, carb to reed block etc] as it could be an air leak that only becomes significant when warm [ie isn't being masked by running rich on choke etc] Just a thought Will-in-the-mud
November 9, 201114 yr Author What jets are in it? My last combination were; idle jet : 35 Main Jet 124
November 10, 201114 yr My last combination were; idle jet : 35 Main Jet 124 Well your jetting does not sound too far off(as this seems to vary with fuel) might go a bit leaner on the main in the 120 or so range. I presume this thing ran ok at one time on the original jets? Based upon your description of the problem, I am thinking your crankshaft seals may be starting to leak. My bike did similar to what you describe at 2-3 years of age. This seems to be due to ethanol induced fuels. Do you qualify? There is a test you can do which may or may not be conclusive. Find the crankcase vent tube below the carb, pull it out and clean the end, then stick it to your tounge to check for variations in case pressure. There should normally be none, as this is just a vent and only checks the engine side seal. The other seal(mag side) could be sucking air as well and a slight test is to remove the cover and use a short spray with carby cleaner or such to see if there is an rpm change. As we are talking minor leakage here, it may be difficult to detect. As (to me) this possibility seems real as your bike may be approaching 2 years old now and we have seen this issue before, smart money maght be to contact Splatshop for a pair of the "VITON" seals, a magneto puller and a clutch cover gasket along with anything else you might need to just simply "do" them and eliminate that potential problem. It fixed my '07 bike, and that as been well over a year now.
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