February 8, 201412 yr Hi there really need some help I just brought a 2010 sherco st 3.0 works replica when I went to view it last weekend seemed to be fine run OK rode OK etc got it home put it away all week got it out to ride today fired up ran OK for 10 min then started to die on lower rpm til it cut out found out it was flooding took carb apart found floats where sticking cleaned refitted seem OK led it ticking over for ten min then went to ride it pulled away and bang big backfire flames out the exhuast now won't start got spark got fuel got good comprestion 150 psi on tester all it dose is back fire with flames wont start any ideas please
February 8, 201412 yr Try checking the woodruff key that correctly locates the flywheel. If this has sheared it would cause the banging that you describe when trying to kick the bike over as the timing will have slipped. Worth a check !!
February 8, 201412 yr Big bang, Probably sheered the woodruff key on flywheel. If it went bang because of too much fuel it can make the engine fire backwards while the flywheel momentum is going forwards and the key gets sheered. TLTEL
February 9, 201412 yr Author Thanks every one I will be making a tool to remove flywheel at work tommrow so I'll know more then
February 10, 201412 yr Gotta be the woodruff key ... can't see how it could be the stator? Maybe that stator nut was a bit loose?? Best of balance. Neo
February 10, 201412 yr Author Took fly wheel off and half the wood ruff key was in it the other half still in the shaft so if order 2 new ones should be here wensday so fingers crossed
February 10, 201412 yr Make sure there is no damage to either taper, if there is then a you'll need to remove it so the tapers lock together properly. A bit of fine wet & dry will work for the crank, using some fine lapping compound between the 2 parts in a twisting motion will match them up, don't go mad on it though as the flywheel will move inwards on the crank if you overdo it
February 11, 201412 yr Either a duff HT coil or duff stator can cause these kickbacks. As soon as you get the engine running check the timing advances and retards correctly using a strobe light and marks on the flywheel.
February 12, 201412 yr If the flywheel nut was not properly tightened, the flywheel will move slightly on the shaft and eventually shear the woodruff key. When that happens, the timing goes way out and often results in a storing kick back or simply not starting. Usually simply , clean up the shaft and bore if they are scored, replace the key and you are back riding.
February 12, 201412 yr I would say probably just a loose nut that caused it to shear. Something to keep a check on. Good luck with the bike. TLTEL
February 18, 201412 yr Author Hi all thanks for all the help it was just the woodruff key its all fixed and running spot on thanks to every one
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