Poulan lawn tractor with a Brigs & Stratton Engine

rmorman · Jun 1, 2016

Howdy all!
Here is a little background as I understand it. This is on a Briggs and Stratton 40H777. Initial problems began when the "solenoid" on the carb that stops fuel flow when bad. This somehow ruined the ignition switch. While troubleshooting to figure out what my initial problem was, I also accidentally tested that coils incorrectly and ruined them as well. SOOOOO, I got the solenoid on the fuel line fixed and installed a new ignition switch. With 1 new coil, the engine seemed to run good. Today we installed the 2nd new coil and that is where things went wrong. In the short time it ran, it began backfiring through the carburetor and then seemingly locked up. Any thoughts as to what may have caused it and what damage I may have done? Any further info you need?

Thanks,
Russ

T.R.K. · Jun 1, 2016

First, Do you have oil in it? Wipe the dipstick off before you take a reading or else you get a false reading of the oil level.

Backfire through carburetor is usually a symptom of an open intake valve. Or else an exhaust valve that cannot open. Remove the valve covers and examine the rocker arms, pushrods, and look through the valve springs and confirm that all the valve guides are the same depth in the head. If that fails to reveal your problem, you may have to remove the head(s). In that case, I would start with the head on the cylinder where you put the last coil.

P.S. You are not the only one to ever accidentally blow a coil.

Poulan lawn tractor with a Brigs & Stratton Engine

rmorman

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T.R.K.

Well-known Member

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