My Tractor Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
312 Posts
Discussion Starter · #1 ·
What would cause my Cub Cadet to backfire when I power down and turn it off after mowing? This just started happening and should I be concerned?
 

·
My Orange Jane Deere
Joined
·
3,358 Posts
Mine was doing that. But now that I ran Seafome through it stopped. :thThumbsU
 

·
Registered
Joined
·
1,023 Posts
Backfires can be serious.

For quite a while now after idling down a hot engine I'll pull the choke to kill the engine.

Now on the newer engines you're supposed to rev them up then turn off the key...despite that advice I still choke mine off.
 

·
Registered
Joined
·
1,994 Posts
Need to know more. There is a true "Back fire"....which means back throught the carb, and a muffler back fire.
If it's through the carb there are only two possibilities:
#1 Hanging valve....most common. The intake is not seating all the way, allowing the combustion to pop out the wrong direction.
#2 timing is really advanced, causing a flame before the valve closes. usually only happens after doing points, or rebuild and things weren't done correctly.

If it's through the exhaust:
#1 Timing is really retarded...or just poor spark...allowing unburned fuel to build up in the muffler. This can get bad, and blow the muffler up like a bomb.
#2 Carb is running stupidly rich....allowing fuel to build up.....blah,blah, blah.

This is a science, but not "Rocket science". I't either timing/ignition, or carb.
99% of the time, it's ignition. Small engine carbs are not complex...they work or don't.

Do a compression check first...to eliminate the valve.
 

·
Premium Member
Joined
·
5,747 Posts
Verify that the cooling system is clean, a hot engine will exacerbate the problem. It is always a good policy to let it idle for several minutes before shutdown, and that may solve your problem also.
 

·
Registered
Joined
·
1,537 Posts
It's a typical problem with these machines. My Kohler carb has an "anti-backfire" valve that seems to do little.

More then likely you are getting a "pop" through the exhaust. It's happens because there is fuel/air vapor in the exhaust and the exhaust is hot enough to light-off the mixture.

Thing that work to reduces this are:

- Choke kill the motor
- Open the throttle as the engine dies
- Keep the power up when shutting down
- Let the engine idle for a minute prior to shutting down

or my favorite

- Put your fingers in your ears and wait the 5 to 10 seconds for it to happen after shut down.
 

·
Registered
Joined
·
1,917 Posts
Gary is right on. I'd *assume* the tractor in question is a Kohler Command twin equipped 2500 or 3000 series? Very common concern. My 2544 would do it on EVERY idled hot s/d if I let it. Throttled up slightly before killing the ignition prevents it. IMO, it's the nature of the exhaust system lighting off the last blip of unburnt fuel, specific to these machine. OTOH, the Kohler Courage 20hp twin on my Z-Force doesn't after fire at all, but it's got a very large commercial style muffer on it. Too much air and not enough fuel to *POP* I'd guess.

Joel
 

·
Registered
Joined
·
695 Posts
MY Kohler M18 is notorious for doing this after it's been worked hard. Either on shutdown or on restart. Through the muffler and it's loud! I suspect it's running a bit rich. But the main jet is non adjustable on mine.
 

·
Registered
Joined
·
150 Posts
Actually my 2165 with the B&S 16 hp engine will backfire (out the muffler) when it's hot. but only sometimes...
my 2185 with the Kohler 18 hp never does...
Maybe the B&S is due for some new plugs?
 

·
Registered
Joined
·
234 Posts
The most common cause is that when you kill your engine, it still pumps fuel and air mixture in the combustion chamber, which ends up sitting in the exhaust. The exhaust temp is high enough that it ends up heating the fuel and air mixture to a temp high enough that it blows.
2 different ways to handle this.
Easiest is to let the engine idle for a minute. This cools the exhaust. Then throttle up and kill then engine while it is reving up.
Another option is to use premium fuel, which has a higher spontanious combustion temp, but it still may be too low to be effective.
Al
 

·
Registered
Joined
·
305 Posts
Actually my 2165 with the B&S 16 hp engine will backfire (out the muffler) when it's hot. but only sometimes...
my 2185 with the Kohler 18 hp never does...
Maybe the B&S is due for some new plugs?
Your Briggs has a fuel shut off solenoid on the bottom of the carb fuel bowl, they are natorious for getting clogged open. You can try and clean it or replace it.
 

·
chicks mow my yard...
Joined
·
134 Posts
Actually my 2165 with the B&S 16 hp engine will backfire (out the muffler) when it's hot. but only sometimes...
my 2185 with the Kohler 18 hp never does...
Maybe the B&S is due for some new plugs?
that's weird, my 2185 kohler command will backfire out the exhaust everytime when it's hot. i assumed it is just the nature of the beast with the command motor. maybe my climate has something to do with it...
 
1 - 13 of 13 Posts
Top