I have a recent year Simplicity Broadmoor with a 25HP Briggs less than 400 hours on it. It has a tendency to go into a severe backfiring when you shut the throttle down. On the Briggs site they say this is normal and they call it afterfire. To avoid it one should run ethanol free gas, which I do, and slow the throttle down gradually. Sounds like bullshit to me. I had 2 separate 23HP Briggs Inteks on a Conquest, which now runs a Kohler, and those engines never had afterfire. Anyone have a cure for this?
#2
StarTech
What happening is raw fuel entering the hot exhaust during shut after the spark quits firing and then this raw ignites.
Probably the fuel solenoid on the carburetor is not closing on shut down.
Actually it is better to have the fuel solenoid to do the engine shutdown instead killing the ignition coils. This engine keeps burning the fuel as the engine starves for fuel and dies.
Now it does takes a little rewiring to keep the safeties in tack to meets liability requirements.
Sounds like you are getting afterfire while moving the throttle from full to idle. Issue could be an unburnt fuel issue, but could also be the muffler itself that is causing the issue.
Idling down not shutting down, to open and drive thru gates. solenoid not relevant. Fellow on another board suggested one range cooler plug. Will try that.
