I actually own 2 of these machines. Out of the blue the machine I use the most started having issues. It starts up cold as normal and will run perfect for 3-5 minutes. Accelerates fine and idles normal. It will then begin to falter when throttling up. Bucks and spits, if moving fast enough will actually backfire through exhaust, like we used to do with our parents car cycling the key off and on to make a backfire. It will then not idle either. Will crank and try to fire back up and some times will try to run till you hit the throttle and then dies again. It seems to be loss of spark to me. It will always try to run and never becomes complete no start. If it was a fuel issue I think it would huff back through intake. I have cycled the ignition switch back and forth and also the kill switch side to side. But have not searched for any broken wires yet. But seems perfect if you let it set and cool. Bumps do not seem to be related. Any thoughts ?

 

I'd check simple things first such as trying a new plug,check for a cut or chaffed coil wire,check resistance on the plug cap. Must show around 4.8k ohms resistance or it could be shorting out causing the problem.Does sound electrical related,but you can also check the valve clearance .006 intake and exhaust, and check for a flattened exhaust cam lobe as it shares the same cam as the other 425 and 500 engines of that year model that were bad on wear. If these checks are ok and not fuel/carb related,I'd check resistance specs on the stator and other electrical trouble shooting guides from the manual.Easier to pay 10 bucks before you start throwing a lot of expensive parts at it. http://visit.tradebit.com/visit.php/...75/264163829/9