Backfires after shut down 2013 Hustler Super z 35 hp Kawasaki

[MossRoad]

I moved your thread to owner/operating. You'll probably get more replies here.

As Bird mentioned, try throttling your machine back to idle, and then wait 20-30 seconds. Then turn it off. That worked for every machine I have with the exception of a 8.5 Briggs that I had. That would backfire every time at shut down no matter what, but it did lessen it from a BANG to a small pop.

 

[Bird]

As Bird mentioned, try throttling your machine back to idle, and then wait 20-30 seconds. Then turn it off.

Shutting one off at idle was what I did for many years. But that will guarantee a backfire with my current Kohler. I said to throttle back to an idle for 5 to 10 seconds, but then go back to full throttle and turn off the key.

 

[Hatman Tractor]

YI have tried shutting it down at 1/2 and 3/4 throttle and it stills backfires only a little louder.

 

[Hatman Tractor]

Did that help any with the backfiring ?

 

[andrehoude123]

My Kubota zero turn back fires after I shut it off to!

 

[RandyT]

Briggs engines have a common fuel passage for both the high speed and idle jet of the carb, which the fuel shutoff solenoid shuts off when you turn off the key. Koher, and Kawasaki have two separate passages for high speed and idle. When you shut off the key it only shuts off the high speed jet, and not the idle jet, So the engine will continue to draw fuel through the idle jet at shutdown, which is the reason Kohler and mostly like Kaw recommend shutting off the engine at 3/4 to full throttle.

had a customer with a toro timecutter that would always backfire at shutdown, Changed the fuel shutoff solenoid, clean carb, and still would backfire. A couple of years ago the engine on this mower dropped a valve and knocked a hole in the piston. Customer had me install a new engine. and the new engine also backfired. the only thing in common between the engines, was I had to reuse the old muffler.

 

[Hatman Tractor]

RandyT your response makes the perfect sense as to why the backfire happens. I had no idea that Kolar and Kawasaki had both a high and low passage, this would explain why the backfire takes place as the engine is still drawing in fuel from the low idle passage Thank for the tip. :applause:

 

[Redneck in training]

Our Grasshopper has Kohler 27 HP engine. We shut down at full throttle never backfires. The original engine was also Kohler but 25 HP. Always shut down at full throttle. Never backfired.
When you shut down with throttle closed the vacuum downstream of the throttle will suck in gasoline, overfuels the engine then the fuel remaining in the suction tract ignites when suction valve opens because there is still burning fuel in the cylinder. When the throttle is fully open there is no vacuum low enough to suck in fuel from, presumably idle or choke nozzle. Main nozzle gets shut off by a stop solenoid.

 

[Hatman Tractor]

Thank you all for the input that has really helped out with this problem. I have taken all of this advise an tried an experiment and it has worked. On shut down for my engine I pull the throttle back to slow idle for about 30 seconds and then push the throttle to wide open as shut the engine quickly off without even a hint of a pop or backfire.
Thank you all for all the great idea's.

 

[gregarterburn]

Thanks for this thread. I have a new Super Z, and if I forget and throttle back just before turning the key to "off", I get a loud backfire. Now I recall the salesperson telling me to only turn the key "off" at 3/4 throttle.