Briggs and Statton Backfires through carb

[Southern Comfort]

I have a 445677 0476 E1 Briggs Eng on a Husqvarna lawn tractor. Ran fine shut it down and the next day when I tried to start it it backfires through the carburetor. I checked the coils for spark, checked flywheel key all ok. I took carburetor apart and cleaned it. Still backfires. My next thought is valves, but what has me baffled is it ran fine the day before. Anybody have any suggestions?

 

[i7win7]

checked flywheel key all ok

If you didn't pull the flywheel to check the key, then I'd replace the key. A slight bend will cause spark timing issues.

 

[Southern Comfort]

I pulled the fly wheel to check it. Thank you for your help

 

[RandyT]

I would remove the valve covers and check to make sure all the push rods are still in place, and also check valve clearances. If you find a bent push rod then look closely at the corresponding valve because the biggest cause of bent push rods on that style engine is overheating of the head due to debris buildup on the cooling fins and the valve guide will migrate outward the valve caps until the valve can't open causing push rod failure. And in the event of a missing push rod the rod had migrated through the oil passage hole in the head into the crankcase.

Also if you didn't properly torque the flywheel after removal while checking the flywheel key it could of sheared on start attempt.

 

[R134a]

I have a 445677 0476 E1 Briggs Eng on a Husqvarna lawn tractor. Ran fine shut it down and the next day when I tried to start it it backfires through the carburetor. I checked the coils for spark, checked flywheel key all ok. I took carburetor apart and cleaned it. Still backfires. My next thought is valves, but what has me baffled is it ran fine the day before. Anybody have any suggestions?

I have a stand-by briggs generator w/ a Vangard v twin did the same thing. Drove me crazy. Carefully...check valve adjustment. If OK then replace BOTH ignition coils. Yeah I know you checked. I did too and it ran like sh*t backfiring a million times. Changed out both coils and now runs like its brand new.

 

[Southern Comfort]

Thanks for your reply. This Eng is driving me crazy. I have spark on both ignition coils but on a 20k scale I get a reading of 4.90 going from the sparkplug wire and the ground terminal. I don't think I should have a reading. The coils might be the problem because the lawn tractor was working fine the day before and the next day is when I started having this problem.

 

[R134a]

I have a 445677 0476 E1 Briggs Eng on a Husqvarna lawn tractor. Ran fine shut it down and the next day when I tried to start it it backfires through the carburetor. I checked the coils for spark, checked flywheel key all ok. I took carburetor apart and cleaned it. Still backfires. My next thought is valves, but what has me baffled is it ran fine the day before. Anybody have any suggestions?

Mine is propane and started backfiring out of the blue also. Briggs answer to backfiring was to check / adj valves. I did that and fooled with the carb but I knew it had to be timing related. I had both sides showing spark but apparently when those coils get crusty, the don't fire like they should. Mine were original likely 15+ years which is way too old when it sits outside all day.

 

[Southern Comfort]

I guess my next step is to check the valves but what is so confusing is this happened suddenly overnight. Thats why I though it was fuel or electrical related

 

[Southern Comfort]

I should have a reading on my coil going from the spark plug wire to the ground.

 

[Southern Comfort]

Update. I found my problem Bent push rod. Thank you everybody for your suggestions. Now the fun begins