Cub Cadet RZT 50 with Kawasaki FH661V engine: Miss fire under load

[toyota]

Although this mower is several years old it only has 56.1 engine hours are on it. Yup it has always had the backfire when turning it off...more than likely a sharp edge/casting flaw in the combustion chamber not removed before assembly. But now it has the problem of miss firing, spitting, backfiring when under a load. First I simply drained the carb bowl thinking water or a speck of dirt and saw nothing. It ran fine following this bowl drain. But did not solve the problem. I was fixing to check, clean and regap the plugs when I looked online and read about all of these issues about valve clearance, valve guide, ignition module problems and said why not join the forum and ask. In 2010, shortly following the purchase of the mower I saw a California (where else) class action law suite concerning the claimed HP output of the engine being over rated and joined the suite and spent my $19 as a result of the suit. Said to myself, yup, got a great deal on the purchase of the mower but maybe because of the Kawasaki engine a lemon now will bother me each time I mow my yard.

Someone posted the valve clearance to be .004-.006. Is this a cold or hot engine measurement? It seams to be getting plenty of fuel but I will check the fuel pump impulse hose. The ignition module sounds like a buy it and try it proposal. Anyone find the same issues and find a resolution to the miss firing?

Thx, Bill

 

[mechanic mark]

Are you idling engine for at least 30 seconds before shutting down, key off, if not it will backfire. Google: Kawasaki mower engine repair manuals, click on K&T parts house, your engine manual is 12 down, see troubleshooting section 10 in manual.

 

[bertsmobile1]

TO meet the stringent alifornian EPA regulatiosn engine sold there are jetted very much on the lean side so the exhaust does run red hot.
Some mowers even have a platinum plated nickle mesh in the exhaust whic works in a similar fashion to the catalytic converter in your car.
When you turn the engine off, this kills the spark but because you have a carburettor if the engine continues to rotate a few times before stopping it will be drawing in fuel and pumping it back out into the muffler.
This is what causes the backfire in the muffler which is reffeered to as an afterfire and apart from damagig the muffler poses no threat to the engine.

To prevent this unburned fuel escaping and eliminating all life on this planet you are required to have a solenoid valve fitted to the carb to shut off the fuel supply to the main jet.
Yours is stuck or cut off.
Both of which I have been told carry heavy fines should you run foul of the pencil dic.s who enforce this stupidity.

Valve clearences are always check cold, stone cold.
Try running the engine with one plug removed then swap this to the other side . There is a diode between the two coils that apparently goes bad and can cause similar symptoms.
Remove each plug and either descibe it accuratly or post photos of each one