Bad boy rebel w FX1000V Kawasaki

Latium05

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Engine back fires when shutting off. I went to adjust the mixture to more lean but cannot find the lean/rich screws. New mower w about 12 hours. Anyone experienced the same issue?
 

mechanic mark

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Set throttle to low idle for 30 seconds before shutting down, it's in your engine manual.
 

bertsmobile1

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Because the stop function works by killing the spark, the engine does several rotations before everything finally come to rest.
Because of this fuel is sucked into the engine, not burned then blown out the exhaust.
Because the new engines run way too lean, the exhaust is red hot internally.
Thus when the fuel in the muffler gets to a combustion ratio that is right for atmospheric pressure it will ignite and scare the poo out of every one within ear shot of the bang.

To prevent this unburned fuel creating an environmential disaster and ending all life on the planet, a device is now fitted to stop the fuel being drawn through the carb & expelled into the atmosphere.
It is called an "anti-afterfire solenoid" and shoves a plunger up the main jet feed to stem the fuel supply.
SO either this device is stuck open ( very rare ) or still getting power after the engine is shut down or the fuel level is too high and fuel is being drawn through the idle circuit.

You can throttle down for 30 seconds prior to shut down or chase up the actual cause.
Please do not run on low idle for much more than 30 sec or you risk overheating the engine.

However as this is a new mower I would be hot footing it back to the dealer while the mower is under warranty
 

7394

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Set throttle to low idle for 30 seconds before shutting down, it's in your engine manual.

Yep, it's in my Kawasaki manual as well. & I never have any backfire issues.. My Dealer told me I'm not shutting it off correctly, I showed him the Kawasaki manual & he said he NEVER read that before.. Doh..
 

Mower King

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Believe it or not......shutting mower engines OFF at full throttle will / can eliminate backfire issues!
 

DK35vince

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I have a FX1000V on my Hustler Super Z.
It has always backfired (95 % of the time) on shut down, since new. (2013 model)
Runs fine. The shutdown backfire never bothered me any, I simply ignore it.
 

bertsmobile1

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Believe it or not......shutting mower engines OFF at full throttle will / can eliminate backfire issues!

No I do not believe you , convince me you are right .

I made the effort to explain the mechanism which creates an after fire.

You explain why shutting off at full speed prevents after fires.
 

Mower King

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No I do not believe you , convince me you are right .

I made the effort to explain the mechanism which creates an after fire.

You explain why shutting off at full speed prevents after fires.

An engine usually only backfires when it has been run quite some time and is hot, then letting it idle creates more heat along with, at idle an engine runs richer so more fuel is entering a very hot muffler and when the engine is shut off, all that gas ignites in the muffler thus, a backfire is created.
Now at full throttle, the engine is running at its best and is in a leaner or optimum fuel mixture mode, thus no excess gas is entering the very hot muffler, so no backfire happens.
You will also find that if you start... and shut off your engine at full throttle, your results will be much better all the way around.
Try this....you will see!
 

bertsmobile1

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An engine usually only backfires when it has been run quite some time and is hot, then letting it idle creates more heat along with, at idle an engine runs richer so more fuel is entering a very hot muffler and when the engine is shut off, all that gas ignites in the muffler thus, a backfire is created.
Now at full throttle, the engine is running at its best and is in a leaner or optimum fuel mixture mode, thus no excess gas is entering the very hot muffler, so no backfire happens.
You will also find that if you start... and shut off your engine at full throttle, your results will be much better all the way around.
Try this....you will see!

Engines have not run richer at idle for near 20 years and definately not since the fixed idle jets were introduced.
Muffler runs cooler at idle as less exhaust passes through it per unit of time ( put a thermometer on it )
The engine itself runs hotter at idle but most of that is in the head & underside of the cylinder.
To ignite the fuel in the muffler creating an after fire you need an air fuel ration of around 14:1 to 16:1 plus an ignition source which is usually a red hot section of the muffler, typically a catalytic converter mesh.

It is not excess fuel that is creating the aqfter fire it is ALL the fuel as the magneto does not spark but the carburettor still is still supplying an air fuel mixture to the cylinder till the solenoid rams that plunger up the main jet.

The OP was not having backfires in the muffler when running , it was an after fire when shut down.
Two different situations.
 
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