Ride on back-firing

[Woodworks]

Is it normal for a ride on mower to backfire? We are not talking little pops but big fat bangs like a gunshot. The engine is a 7.3 kw Briggs and Stratton.

 

Any help appreciated

[Rich2484]

Yeah it's a Briggs and Stratton.

 

Any particular time it does it. They are known to do it on starting when warm.

[Stubby]

Hole in the exhaust or valve clearances too tight ( exhaust valve not seating , fuel getting into exhaust and igniting ) or timing out ..........

[GardenKit]

Beau, it should not backfire if you let it idle for a while after using, but then increase the revs to between 1/3 and 1/2 speed before turning the ignition key off.

 

The electric fuel stop solenoid will cut off the fuel through the main jet if turned off in this fashion, but if turned off in the idle position it will continue to drag some fuel through the idle jet which is unaffected by the solenoid. Any such fuel is then reignited by any hot spots in the exhaust. These hot spots will become less active with age as the exhaust cokes up.

 

Its not just a Briggs thing, the single cylinder Kohler is just the same.

[Rich2484]

Beau, it should not backfire if you let it idle for a while after using, but then increase the revs to between 1/3 and 1/2 speed before turning the ignition key off.

 

The electric fuel stop solenoid will cut off the fuel through the main jet if turned off in this fashion, but if turned off in the idle position it will continue to drag some fuel through the idle jet which is unaffected by the solenoid. Any such fuel is then reignited by any hot spots in the exhaust. These hot spots will become less active with age as the exhaust cokes up.

 

Its not just a Briggs thing, the single cylinder Kohler is just the same.

 

I know. Just hate the Briggs and Stratton :lol:

[thtc]

if its back firing alot check then valves and the clearances as if they are not closing correctley or tightly enough then to much fuel will be going through and igniting in the exhurst. try a good dose of petrol cleaner in with the fuel and run it hot, it should blast out a good cloud of black smoke, if it does then the valves and internals are pretty clogged up