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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 28896
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have and 18 HP icy twin .Engine Briggs & Stratton 18 HP

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I have and 18 HP icy twin .Engine
Briggs & Stratton
18 HP twin I/C
Model 422437
Type. 4145 L1
code. (###) ###-####JA: I'll do all I can to help. How long have you been dealing with this?
Customer: The engine runs and then stalls sometimes backfires and keeps running
JA: Can you guesstimate how old the engine is? And has it done anything like this in the past?
Customer: Approximately 12 years old
JA: Do you plan on doing the work yourself?
Customer: it did this in the past and I rebuilt the fuel pump which took care of it
JA: Anything else we should know to help you best?
Customer: I just finished rebuilding the fuel pump again and it's doing the same thing
Customer: replied 28 days ago.
I also flushed the gas tank and fuel lines and put in a new in-line filter.

Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!

This is the older flat head design engine. Have you checked the valves for clearance? It has to have some, .006 in is the gap. But it will work ok, as long as it is not zero. To get to the valves and tappets, you have to remove the intake manifold, t get the crankcase vent cover off of both sides.

Curtis B. and 2 other Small Engine Specialists are ready to help you
Customer: replied 28 days ago.
I have not checked that . The problem came on very suddenly and didn't seem relative to wear. It's been running beautifully open till my last mow when it started this backfiring and dying out

Ok, may not be valves, run cylinder test and see if it is related to one cylinder. Loosen the spark plug wires,and with engine idling, remove one wire at a time. If engine dies when one wire is removed, the opposite cylinder is not firing. Run compression test, to see if a valve is stuck open.