why is it backfiring through the carb when starting?
i rebuilt the carb on a 8hp motor. Also put a new coil on it. It has fresh gas in it . compression was 74lbs. It was running fine before it lost spark. i was wanting to know what the valve clearance was on both the intake and exhaust valves.Also what the compression should be. It was not smoking, it is on a log splitter
Asa general rule briggs engines are 4 thou inlet, 6 thou exhaust. Set piston 1/4" past TDC to get them right. Is flywheel key intact - if it kicks once and shifts on the key iot will continue to backfire aftewards.
eparkmowers, January 2009
The compression of 74lbs should be fine...!
Tony, January 2009
check the ignition timing it may be out, it may also just be that the carb is too lean, screw in mixture screw and then screw out 1-1/2 turns counterclockwise.
move engine control to run engine at normal operating speed.
turn needle valve in clockwise until engine starts to lose speed (lean mixture).
then slowly turn needle valve out counterclockwise past the point of smoothest operation until engine just begins to run unevenly (rich mixture).
turn needle back clockwise to mid-point (smoothest operation) between rich and lean mixture.
final adjustment of the needle valve should be slightly to the rich side (counterclockwise) of the mid-point.
Tony, January 2009
edit
I can answer this question...
why is it backfiring through the carb when starting?
