Backfiring

[John R]

I finally got to use my new Tiger Cat II (FX 730 V) engine, I ran it about 30 to 40 minutes at full engine speed cutting and when I shut it down it backfired out the exhaust, I did let it idle for a few minutes for cool down before stopping.

Is this a problem, or is it just the nature of the beast?

 

[BlazNT]

Read the manual it will tell you where to put the throttle before turning it off.

 

[John R]

The manual only states to let it run at an idle to cool down before shutting it off.
Might be because it's still new, only have about an hour on it

 

[BlazNT]

My manual told me to back off to 3/4 throttle then wait a few sec then turn off. But I have Kohler.

 

[John R]

Mowed yesterday, took about an hour, backed the mower into my lawn shed, let it do a cool down idle for about 1 minute, shut off key and bang, loud as hell, going to get a hold of my dealer on Monday and see if there is something he can do.

Went out and tried it again, very loud backfire when shutting the engine down, sounds it's going to blow the muffler off.

This can't be the way it's supposed to work.

 

[bertsmobile1]

The fuel shut off solenoid is not working.
These are expensive little critters so take it back to the dealer.

 

[John R]

The fuel shut off solenoid is not working.
These are expensive little critters so take it back to the dealer.

I can hear and feel it click when turning the key switch on and off, is there a way to check it like maybe seeing if the engine will start with it being unplugged?

I went out and started the engine, then unplugged the solenoid and the engine quit, not immediately but it did quit.
So does that mean it's working?

 

[ILENGINE]

Think of it this way. When you turn the key off it kills the spark. From your test, the fuel isn't getting shut off immediately. that fuel is getting pumped into your hot muffler and getting ignited by the air when you shut off the engine.

 

[John R]

Think of it this way. When you turn the key off it kills the spark. From your test, the fuel isn't getting shut off immediately. that fuel is getting pumped into your hot muffler and getting ignited by the air when you shut off the engine.

In the years past before the EPA started screwing things up, carbs didn't have these and the key just shut off the spark, there was no backfire, why now?.
I'm not doubting what your saying, just don't understand it.

 

[bertsmobile1]

In the years past before the EPA started screwing things up, carbs didn't have these and the key just shut off the spark, there was no backfire, why now?.
I'm not doubting what your saying, just don't understand it.

To comply with the new EPA requiremants the modern engines run verging on too lean.:thumbdown:
Lean = hot
Very lean = really bloody hot.
So the muffler internals now run at red heat.
Some even have an afterburner ( called catalytic converter ) in them that glows red hot for quite a while after the engine stops running.

Thus now days you have fuel +air+ ignition source = bang.