Mowing Does your Lawn Mower or Garden Tractor made a loud

TRD · Jul 4, 2005

Backfiring (or more accurately "afterfire") is caused by unburned fuel/air mixture being ignited by the heat of the muffler. When the ignition switch is turned to the OFF position, the spark to the spark plug stops immediately, although the engine continues to rotate for a short while afterwards. As a result of this engine rotation, more air/fuel mix is pulled through the carburetor. Because there is no spark this fuel is not ignited in the combustion chamber as it normally is. This mixture can then build up in the hot muffler and ignite. The loud bang heard is the sound of this fuel igniting after the engine has shut off. Allowing the engine to idle from 30-60 seconds before turning the key to the OFF position will generally prevent this afterfire condition. Engines equipped with an electronic fuel shutoff solenoid have an extra valve that shuts off the fuel system immediately when the ignition is stopped. These models should be turned OFF with the engine at FULL throttle. The length of time it takes for these engine to come to a complete stop is generally long enough to flush out the residual exhaust mixture, but there is no raw fuel to ignite in the muffler. There are several other factors involved such as; ambient temperature, fuel additives, carburetor settings, alcohol enriched fuels, etc.. that may also contribute to the afterfire condition. These are only suggestions, a service dealer will have to make the final determination as to the exact cause and best remedy for each individual engine design and application.

maxtor1 · Jul 4, 2005

idle your engine down for about 30 seconds before you kill it. i think that will help your afterfire.

JTKub · Jul 4, 2005

My 2544 will BANG most of the time if you shut it down at idle (once its hot). Kill the ignition anywhere from just a blip above idle to full throttle & it's fine. One thing that will startle you, is if you trip the seat switch while on the fly. This only kills the ignition & PTO, but not the fuel cutoff soleniod. You can get one heck of a KA-POWWW!! in that situation. I've nearly had to change my drawers once or twice. /forums/images/graemlins/tongue.gif /forums/images/graemlins/shocked.gif
G/luck
Joel

Ed_S · Jul 6, 2005

Here is a question - which models have the fuel shut off??

On my 2523, the ONLY way I have found to prevent the after fire, is to idle as described and then while turning key to off, move throttle to WOT as the engine dieing.

Ed

cubmaster · Jul 6, 2005

I can leave mine (2523) at 1/2 throttle and no backfire, I think it also says to do this in the owners manual.

cyberkrazze · Jul 13, 2005

I think all of the models now have the fuel shut off. We have sold hundreds of lawn tractors throughout the years, and we get one once in a while that will back fire on shutdown. Try putting your throttle at different positions before shutting down. We have had a few engines that would only not backfire if you turned it off at full throttle. This is what we were told by the tech guys at Cub.

OhioGuy · Jul 17, 2005

I've owned 5 Cubs starting with a 149 and currently have a 1872 and a 5252. They were all Kohlers and they all backfired. Not everytime, on occasion you'd be walking away from the tractor and BOOM. Really startles you. /forums/images/graemlins/shocked.gif

I always thought idleing them down made the most sense, I'll have to try some different throttle positions.

Thanks!
Curt

JPPWNY · Jul 17, 2005

Definitely setting doiwn the throttle and letting the engine idle at slow speed before shutting off the engine prevents backfires.
I actually set the throttle all the way down and let the engine run at that setting for a bit and then turn off the tractor. Haven't had a backfire yet.

JTKub · Jul 17, 2005

</font><font color="blue" class="small">( Definitely setting doiwn the throttle and letting the engine idle at slow speed before shutting off the engine prevents backfires. )</font>

You must have a special kohler then /forums/images/graemlins/confused.gif /forums/images/graemlins/wink.gif. All the anti-backfire solenoid equipped- kohler and briggs engines I've owned or used backfired on an idled s/d. Per the ops manual(s), they all needed to be throttled up prior to s/d.
G/luck
Joel

JPPWNY · Jul 17, 2005

My JD Briggs and Stratton has backfired on me twice this year even with the throttle idling low.

My Cub's Kohler has only backfired when I forgot to shut off the engine and got up out of the seat to pick up a deer antler.