July 9, 20188 yr Hi, Advise please..? I recently purchased a 290 Sherco to ride with my lad, bike pulls well in low to mid range.. if attempting a large climb the engine will not rev out, I guess it sound like piston slap is the only way I can describe..? - the bike does rev up in neutral though and sounds normal.. ............................................. Andy advise welcome before I start stripping the bike.. Thanks in advance. Shutt01
July 9, 20188 yr Lack of fuel? It does have the fuel pump. Try it with the tank completely full. That helps sometimes.
July 9, 20188 yr Author Thanks for the reply, Hears what I have tried tonight 1, Spark plug check - looks tanned and gap reset - nice blue spark 2, HT Cables checked - looks new internally 3, Air Filer looks clean - no blockage .......................... It doesn't feel like fuel starvation - it feel more mechanical, then I guess The bike runs clean in neutral but as soon as any load in any gear above approx. 4k rpm the bike pulls back with bad noise from top end of engine.. .......................... Have I bought a dud bike..? Thanks again for your advise/. Regards Shutt01
July 9, 20188 yr From your description it does look like you may have a worn big-end, diagnosis at a distance is difficult of course and I may be wrong. Have you checked the ignition timing? If you take off the flywheel casing you can rotate the flywheel by hand back and forth, listening for any untoward noises. While the case is off try for sideways, up and play this will indicate the condition of the main bearings. Another fault to check for is detonation or the layman’s term is pinking, sometimes brought on by excess carbon glowing on the piston crown combustion chamber. This causes the fuel to start to burn too early and then the fuel literally explodes and makes the piston rattle like a bolt in a tin can being shaken; continued detonation puts tremendous pressure on the piston crown and it was never designed to suffer this....a hole will be burned in the crown or the piston may crack. There’s lots more but I think you have enough to be getting on with, just investigate methodically as you have been doing??
July 10, 20188 yr Mains and the rod bearing would make noise just running. Pinking it could be, but the fuel pump could just be going lean with an air leak. It is a crap system only found on the Sherco. (Unless you count snowmobiles.) i would use an auxillery fuel tank just to rule out that whole system. Edited July 10, 20188 yr by lineaway
July 10, 20188 yr A exhaust that has carboned up will choke the top end,possibly to the point of causing detonation. Symptom is a loud exhaust as it clogs all the "pores" of the silencer and creates a 4 foot straight pipe effect with no exhaust tuning. 2 strokes do not care for straight pipes longer than 10-12 inches. What year 290? I have put the later model repackable exhaust on a 2011 and a 2013,requires the matching header also.
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