craftsman 19 1/2 HP

[whitehouse]

Hello, new member needing help.
my Briggs 19 1/2 HP surges all the time and backfires frequently no matter what the rpm. I tried adjusting fuel but didn't help. Carburetor has been cleaned. all ports open.
any ideas?

 

[motoman]

whitehouse, Don't know your machine. If it has adjustable valves check them, governor working if present? Perhaps partially blocked fuel delivery which starves and catches up?

 

[DaveTN]

Overhead valves sometimes get out of adjustment like the other mechanic said. Could also be a partially sheared flywheel key causing it to be
slightly out of time constantly backfiring...yet in time enough to run. Spark plug coil could also be weak. Years ago when we had points and condensers,
a bad condenser would cause a terrific backfiring. Nowdays it's all electronic. Could also be a partially sticking Intake Valve not seating properly
causing backfiring. Just have to check things, measure the valve clearances etc. Good Luck!