dan1 Posted January 7, 2018 Report Share Posted January 7, 2018 So basically I was out a couple weeks ago then the bike started to rev really high and the kill switch wouldn’t work then it just cut out and wouldn’t start again. Kicking it felt like it had lost some compression so I took the head off to find he piston rings were melted and the side of the piston was all scratched. So I ordered a new piston, fitted it then tried to start it, compression is good but it just keeps backfiring when trying to start? Any ideas? Quote Link to comment Share on other sites More sharing options...
dan williams Posted January 7, 2018 Report Share Posted January 7, 2018 Sheared off woodruff key on the ignition flywheel. Fairly common occurrence. If the woodruff key didn't shear you run the risk of twisting the crank so it's actually a protection mechanism for the engine. 2 Quote Link to comment Share on other sites More sharing options...
v1nn1e Posted August 15, 2018 Report Share Posted August 15, 2018 I've been having some ignition problems with my 2011 and tracked it down eventually to the ignition coil. Meanwhile I'd been down the stator route and so had removed and refitted that. Got the bike running but not that well and cut out completely on Map 2. Then when running on Map 1 noticed that the exhaust was getting very hot. Decided to re-check that I'd got the stator marks aligned correctly (maybe ignition timing advanced) and on removing the flywheel discovered to my horror that the woodruff key has sheared! What can cause that? Did I overtighten/under tighten the crank nut? It certainly didn't need as much leverage as I was expecting to undo - I don't think I quite managed to reach the full fat 100nm or torque when tightening. Now got to hunt down a new woodruff key - but reluctant to simply re-assemble until I've understood why this has happened!!!!???? Quote Link to comment Share on other sites More sharing options...
misterroy Posted August 22, 2018 Report Share Posted August 22, 2018 The woodruff key is only there to align the flywheel during assembly. It is the taper that holds it in place relative to the shaft. You need to lap the flywheel to the shaft. It does not take much to do it. I havent watched this video, but I think it is what you want. Quote Link to comment Share on other sites More sharing options...
v1nn1e Posted August 28, 2018 Report Share Posted August 28, 2018 Didn't go as far as lapping-in the flywheel but did give it and the crankshaft taper an extra good clean with meths, and then upon re-assembly a sharp tap or five with a rubber mallet to make sure it was well seated. Have not had any problems since. I believe one issue is that the magnets mean the flywheel 'pulls' itself on as you start to line up the channel with the woodruff and one can think it's all done, but regardless it needs that extra good tap with the mallet to really bed it on to the taper. Cheers Quote Link to comment Share on other sites More sharing options...
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