Engine backfires

" I have just rebuilt my 150hp

" I have just rebuilt my 150hp motor (john,150,v6,late eighties)after replacing all gaskets in carbs, head, and fuel vro pump.I didnt adjust the timing yet as i am waiting for a timing light, but I started it from its old timing and found that when im starting it its inclined to give a backfire during startup,it will then run for a bit then stop usually with a backfire,is this a sign that the timing is way out? I also notice that when Im priming with the fuel bulb prior to starting,I can still hear fuel squirting around the vro pump after the carbs have filled and the bulb should normally get rock hard it can still be squeezed! there are no visible leaks, could the fuel be getting in to the manifold some way causing this backfire?

Your thoughts please guys!

Thanks.Bob "

usually the backfire means th

usually the backfire means that the timing is way out..it could also be that your reed valves are opening and closing at the wrong times

"Bob.... If you're speakin

"Bob.... If you're speaking of a regular backfire, the loud type that's firing out the exhaust, I would suspect that you either knocked the flywheel/crankshaft key out of place when you installed the flywheel, or you did not torque the flywheel nut properly, which would result in a sheared key and damaged tapers to the flywheel and crankshaft.

Torque for the 35amp charging system flywheel is 145 foot pounds, all others are 105 foot pounds.

I would strongly suggest that you block the fuel hoses off, one by one, and find out where the fuel is excaping to. I've seen boat fires, you don't want one!

Joe "

" Bob,
I had the backfire pr

" Bob,
I had the backfire problem with a 1978 55 Johnson. It was a sheared woodruff key for the flywheel. I think Joereeves hit the nail on the head on this one. "