Have a ZT Husqvarna 23hp intek v-twin mower that backfires through the exhaust. does it most after mowing idling down putting away for the day, but some during start up.
Have checked the Flywheel key- was not bad, Used heavy doss of Sea foam in gas and some in oil- no help, have read could be Coil wire harness Diode problem, Carb problem and or Valve issue.
Don't know which to check first.
Any suggestions?
Tskinner
If you get a loud bang in the exhaust after then engine has stopped revolving, the carb solenoid is not working.
Preventing this happening is the lie peddled to Joe Public about the addition of this high cost item to their engines.
Explosions in the exhaust happen because unburned fuel is coming out of your engine and entering the exhaust where it gets diluted with air till it gets to a combustable air fuel ration when it ignites and goes bang.
So you are looking for reasons why you have unburned fuel coming out of your engine.
A bad plug is the No 1 suspect
Bad exhaust valve sealing is No 2 suspect
Blown head gasket is No 3 suspect.
There are a lot more but all of them manifest themselves in poor to difficult running and have other symptoms.
So start with some nice new plugs and check they are properly gapped.
If the gap is too wide then the spark is retarded so you can still have burning fuel happening in the cylinder when the exhaust valve closes .
Next remove the solenoid and check that it retracts & extends fully as you turn on & off the ignition key, do this 20- 30 times.
It is a needle valve so check the end of it for damage and the end of the main jet tube it seals against.
These are the easy bits that require no special tools nor much in the way of mechanical ability.
Next remove the blower housing , clean the fins and check the wiring for damage, you should do this at the beginning of every season in any case, particularly is you have mice in your area ( find one that dosn't )
Follow that with a leak down test to check the integrety of each cylinder. This does require a special tool and an air compressor ( one that plugs into your cars lighter will be fine ) and a tester is easy to make ( lots of how to's on you tube )
