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Hi, just rebuilt a li150 series 2. Got the 12v kit working correctly now and all I get is a backfire now and again when kicking over. It won’t fire up, any suggestions? Thanks

woodruff key sheared....maybe ?

Should be fine as all new

Very easy to shear it even a new one. Has it run OK and just started to backfire. I have sheared mine by not doing the flywheel up tight while strobing it up. It’s a clear sign the timing is out.next you look at stator pick up and does it line up with the flywheel. Lots of combinations of parts being supplied these days.

MickYork wrote:woodruff key sheared....maybe ?

+1 , done it a few times by not tightening up the flywheel nut properly

MK Monty wrote:Very easy to shear it even a new one. Has it run OK and just started to backfire. I have sheared mine by not doing the flywheel up tight while strobing it up. It’s a clear sign the timing is out.next you look at stator pick up and does it line up with the flywheel. Lots of combinations of parts being supplied these days.

This is the first time to try and fire up after full rebuild

I would double check your timing marks and re-strobe

What type/make ignition system?

What does the compression feel like and is it a sharp backfire or more like a wet fart. Low compression can result in a wet bacfire as the gasses escape past the rings

coaster wrote:What does the compression feel like and is it a sharp backfire or more like a wet fart. Low compression can result in a wet bacfire as the gasses escape past the rings

Given the new rebuild though, the woodruff key as already mentioned would be the prime suspect as it is itting thre very easy to dislodge it when fitting the flywheel. been there etc

Head Gasket / Seal ??

Toddy wrote:Head Gasket / Seal ??

Yes I would suggest checking this as well,purely because I had similar symptoms on my TS1 a few years ago and after wasting loads of time and effort on carb and electrics it turned out to be head gasket

rodney wrote:Hi, just rebuilt a li150 series 2. Got the 12v kit working correctly now and all I get is a backfire now and again when kicking over. It won’t fire up, any suggestions? Thanks

Had almost identical problem that baffled me.Despite being doubtful of the majority of advisers pointing to the Woodfruff key being the cause. I nevertheless followed the
strong opinion and indeed found the new woodruff key had sheared and upset the timing.On replacing the part I also followed advice to lap the flywheel to the shaft. This welcome advice saved countless hours for which I'm still grateful.
Please advise any problems found when up and running.
Regards.

Backfire has gone, checked woodruff key and reset timing now I get nothing at all. Got spark and fuel but she just won’t fire up. Thanks for everyone’s help

rodney wrote:Backfire has gone, checked woodruff key and reset timing now I get nothing at all. Got spark and fuel but she just won’t fire up. Thanks for everyone’s help

Any joy yet, interested to see if your problem was solved. I too had problems after a rebuild, not backfireing but just would not start, turned out to be gaskets. Cause I hadnt done the leakdown test properly.