Backfire

[89retta]

I have a 77 140hp.It backfires when trying to start it.I've set the timing according to joe reeves method.Pulled the intake off reeds are ok.I have not checked the flywheel key.With the tdc mark on the flywheel lined up with the timing pointer should the #1 piston be at or near the top of cylinder,Thanks for any help

 

[Joe Reeves]

Re: Backfire

If the engine is really backfiring, that is firing out the exhaust and sounds like a shotgun blast, that can be caused by......

Coils hooked up to the wrong cylinder.... powerpack orange leads connected to the wrong coil.... timer base leads connected to the wrong terminal of the powerpack, BUT......

The most likely cause is a sheared flywheel key. The flywheel nut must be torqued to 105 foot pounds. Anything less results in a sheared key. If this is the case, make sure you clean up the flywheel and crankshaft tapers, then install the proper 307480 key, NOT a look alike key from a hardware store. The key must be installed straight up and down (vertical outer edge), NOT aligned with the crankshaft taper!

 

[89retta]

Re: Backfire

Thats what i was thinking.When i do have the tdc mark lined up with the pointer the #1 piston is near the bottom and #4 is near the top.

 

[boobie]

Re: Backfire

Sounds like a sheared flywheel key.

 

[89retta]

Re: Backfire

Pulled it off and it was sheared.thanks for your help.