09 Big Bear 250 Backfire
 

Hey guys, I just picked up a 09 Big Bar 250 that was completely taken apart. The owner was trying to fix a no spark issue. I put it all back together and sure enough no spark. I have had a Timber wolf, 3 Bear Trackers, and Bruin 250 over the years so yeah I like these things. After a ohm test on the stator sure enough dead pickup coil, so I ordered a fleabay special. I have put one of these on a couple of the other quads with good results. Anyway, the stator came today and I installed it right away. Quick check and sure enough nice spark. Hook everything up and no start, but a nice backfire through the carb. Clean carb,, no start. Check compression (120psi) no start. Hit it with starting fluid and it back fires real bad, you can hear the starter one way clutch complain. Try pull start and it really jerks your arms. I pulled it back apart and checked flywheel key. Lined up timing marks and they are spot on. Set valves to .004 intake, .005 exhaust. It seems like it is firing on the wrong time. But there is no way to do that, that I can see. Could the new stator pins be backwards? Would it spark but out of time? I am stumped. It doesn't even try to start just bad backfire through the carb. Ideas?

I have heard that the wires from the pickup coil can be backwards, which I assume, will alter the timing. Worth swapping them to see. I guess the makers could get the physical position of the coil wrong. Also. of course the flywheel can slip, which throws ignition timing out. See if TDC by the piston is TDC by the flywheel mark. Difficult to tell within 5 degrees but a slipped flywheel is usually well out.

Merryman, that is what I was thinking too. I saw a thread somewhere when researching how to test the stator that mentioned something about this. I was searching and couldn't find it. I will switch the wires today and if that fixes it I will update everyone for future searches.

Well, that was the problem. Switched the wires and it fired right up. Now I have the classic intake boot leak. Next...