Why do my Kohler engines backfire when shut off?

[bczoom]

I have 2 machines with Kohler engines.
Garden tractor with a 18hp 2 cyl Kohler and a ZTR with a 23hp 2 cyl.

If I run them at higher RPM's (mowing) but don't let it idle for a few minutes before shutting them off, they let off one heck of a backfire.

Why is that? I have no other engines (Honda, Subaru Robin, B&S...) that do the same thing.

 

[Bob_Skurka]

Thinking about the 4 cycle engines I have now, here is a rundown of what I can recall:

2 cylinder (opposed twin) 18hp Kohler that never backfires (on a Cub GT).

5hp Briggs that backfires every time it is turned off (on a Yardshark chipper) but runs fine otherwise.

2 cylinder (V twin) 18hp Briggs Vanguard that never backfires (natural gas generator).

Last spring I got rid of a MTD rear tine tiller with a Briggs 5hp (?) engine that backfired constantly when shutting it down but ran great otherwise.

I have a 6hp (?) Kawasaki on a 12+ year old JD lawn mower that runs perfectly and probably backfires less than once a year. I also have a Kawasaki (21hp) gas engine in the Ventrac GT and that has never backfired that I can recall.

 

[briggs_man]

</font><font color="blue" class="small">( but don't let it idle for a few minutes before shutting them off, they let off one heck of a backfire.
)</font>

Well you just answerd your own question,,,, Plain as day states in my Kohler shop manual and operators manual . Engines WITHOUT the fuel shut off soloenoid in the carbarator to Let Place throttle at low idle and let engine run 30-60 seconds then shut off engine ,,,,,,, My 25 hp twinn if not idled down will not only afterfire but also diesel up a storm so every operator now sees a tag taped to the dash about shutdown .

 

[wushaw]

I have a 15hp Kohler on a ZTR and I let it idel for about a minute before shutdown and it has never backfired yet. It's all in the shutdown procedure.

 

[pajoube]

I have a 25 hp Kohler and if I do not reduce the throttle and let it run for a few seconds at low RPM it will continue to chug, chug after key turned off. By doing the above it will shut down almost immediately.
PJ

 

[B2400]

When you shut the engine off( especially from a high rpm) you load the exhaust with raw gas fumes. The exhaust is hot and ignites these fumes, thus you get a loud "pop" thru the exhaust.

 

[KENSFM]

A bad exhaust valve or too lean a fuel mixture will also cause an engine to backfire. For some reason Kohlers do seem to backfire more than other makes.
Ken /forums/images/graemlins/smile.gif

 

[zapper]

I also have a backfiring kohler on my ZTR Grasshooper (which only happens on shutdown). This has been going on since the unit was new so I contacted Kohler. The represensitive said when turning off the engine turn the rpms up (vs idle) and this seem to solve my problem.

 

[GerardC]

<font color="blue"> The represensitive said when turning off the engine turn the rpms up (vs idle) and this seem to solve my problem. </font>

On occasion my Briggs would backfire. I tried turning the idle up (all the way) and then turn the key off (right away). We never get a backfire doing it like this. Sounds like you got good advice.

 

[Bird]

I can't claim to know much about these new engines. All my life I've let engines idle briefly before turning them off. However . . . , when I tried out the Toro ZTR with a 14hp Briggs engine, I pulled the throttle back to idle, turned off the key, and was startled by a terrific backfire. /forums/images/graemlins/shocked.gif The dealer was standing there and said, "Yeah, they all do that; you're supposed to shut it off at full throttle." /forums/images/graemlins/shocked.gif Now I'd never heard of such a thing, but to quote my manual:

" Stopping the Engine

1. Move the throttle lever to Fast

2. Move the PTO to Off

3. Turn the ignition key to Off"

Now I've tried it a couple of times since I bought it. If you turn it off at idle, you wonder if it's going to blow the muffler off, but if you turn it off at full throttle, it dies quietly and smoothly, as it should. /forums/images/graemlins/confused.gif