OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Honda Engines honda hru196

why does the engine backfire when the throttle is moved quickly from RUN to IDLE. It is 2yrs old.

Does it perform correctly when you move the speed control at a moderate rate? If so, chances are the carburetor and governor do not work and play well together under extreme conditions. The classic way to achieve a backfire (which is a gas explosion in the exhaust pipe or muffler) is to run the engine at high speed, then switch the ignition off briefly then on again whilst keeping the throttle open. Sometimes the muffler bulges or bursts under those conditions. Now that cars have catalytic converters, such stunts can become very expensive and are best avoided.
If your engine has an ignition kill function that is activated by setting the speed control at minimum, it is easy to imagine the control over-travelling slightly and briefly shutting off the ignition, then letting it resume.

No backfire occurs when throttle is closed slowly.
Idle & stop position of throttle lever appear to line up with original marks.
thanks derf

derf,

Have you tried a new spark plug to see if corrects the problem.

Bruce,
I have tried a new plug with no change.
I am re-visiting the gov. setting & throttle combo. as suggested by " grumpy"
I will keep you posted.
thanks again derf

derf, if it isn't a momentary interruption of the ignition when you snap the speed control to minimum, there are several less likely things we can work through. They center on some combination of leaky exhaust valve and rich idle tuning, but that usually results in fairly mild pops in the muffler rather than hearty bangs - and your mower doesn't seem old enough unless it has been in heavy contractor service during those two years.