Bad gas?

[ArlyA]

Gasoline that's a few months old has likely gone bad. Smell it, if it smell funny, its bad. In warmer temps, it can go bad in far less than 2 months.

Good luck!

Gas is a few months old. (Someone else filled it.)

Engine: 24HP/724cc Briggs & Stratton Endurance Series V-Twin Engine

I believe the choke was operated correctly. On while starting, just for a few seconds.

Leaking oil: Not that I can see. It's a less-than-2-year-old tractor with light use, so I hope not! However the main engine clutch was just replaced.

 

[GirlWhoWantsTractor]

Great. Imma make Jay syphon it out since he filled the tanks. City boy.

 

[plowhog]

What is the operating and service history of this unit? Sounds like a *lot* of repairs.

I agree with changing the gas-- first thing. Many years ago I was flying a Beech B55 Baron twin engine plane and the engines were doing lots of really bad things. Very disconcerting especially right after takeoff. The fuel was sampled and checked out fine. But I had 90 gals drained out despite it checking out OK ($5/gal) and then refueled. The problem went away. I hope your resolution is that simple.

 

[GirlWhoWantsTractor]

What is the operating and service history of this unit? Sounds like a *lot* of repairs.

Bought new in 2016. Motor clutch fell out in first week. Then two other fails before first 50 hour service. etc. etc.

Serviced twice a year by dealer (spring and fall).

Used primarily for mowing. Also pulls a DR leaf vac a few times a year. Also some driveway grooming with a small rear blade.

Spends winter in the barn, most of the rest of the time in the shop.

 

[zzvyb6]

"Sounds" like there is a hot-spot in the cylinder that is dieseling after you shut off the ignition and during operation for a while. Wrong spark plug, object in cylinder, hot valve(s). I had a kohler that did it. Jumped valve timing caused pre-ignition.

 

[1010]

I'm going with a lean gas problem, that could be from a dirty fuel filter, or jet in the carb, the question is, bad gas varnish or trash?

If it's varnish from bad gas, Sea Foam added with fresh gas can help with getting the engine back to normal.
and change the fuel filter.

WARNING, if you have varnish in the tank, lines and carb, adding sea foam will break all that crap free and the mower will probably won't run at all. And everything will have to be removed and cleaned, Sea Foam is either going to help, stay the same because varnish isn't the issue or it'll clog up everything.
Try tapping on the carburetor and see if that'll allow the float inside to drop down and allow more gas flow. If you get gas out of the air filter it's stuck open and not cutting off the gas. A sign of varnish or trash.

Will the mower run somewhat normal with the choke pulled out, I don't mean idle, I mean with the throttle opened up a fair amount and the choke pulled out some not all the way? With the mower running try moving the choke in and out and see it that clears up some of the popping. If it does you have trash or varnish in the carb. You can get sea foam at the parts store wal mart might have it also.

Don't buy ethanol gas for small engines.

 

[GirlWhoWantsTractor]

I'm going with a lean gas problem, that could be from a dirty fuel filter, or jet in the carb, the question is, bad gas varnish or trash?

If it's varnish from bad gas, Sea Foam added with fresh gas can help with getting the engine back to normal.
and change the fuel filter.

WARNING, if you have varnish in the tank, lines and carb, adding sea foam will break all that crap free and the mower will probably won't run at all. And everything will have to be removed and cleaned, Sea Foam is either going to help, stay the same because varnish isn't the issue or it'll clog up everything.
Try tapping on the carburetor and see if that'll allow the float inside to drop down and allow more gas flow. If you get gas out of the air filter it's stuck open and not cutting off the gas. A sign of varnish or trash.

Will the mower run somewhat normal with the choke pulled out, I don't mean idle, I mean with the throttle opened up a fair amount and the choke pulled out some not all the way? With the mower running try moving the choke in and out and see it that clears up some of the popping. If it does you have trash or varnish in the carb. You can get sea foam at the parts store wal mart might have it also.

Don't buy ethanol gas for small engines.

I have some Sea Foam. Will try that.

We buy ethanol-free gas at our local gas station for the tractors.

Remember this is a 2-year-old tractor with low hours that was JUST serviced....

Mower runs somewhat normal only when mowing, although it surges. It starts sputtering as soon as mower is stopped, the slower you go, the more it backfires. Stop the tractor and push the throttle down to low, backfires more and more, like gun shots. Then one final BANG after the engine is cut off.

 

[1010]

With the mower running above idle pull out the choke slowly and see it the popping clears up some.
Everything you describe sounds like a fuel related issue to me. ESP the surging.

 

[GirlWhoWantsTractor]

With the mower running above idle pull out the choke slowly and see it the popping clears up some.
Everything you describe sounds like a fuel related issue to me. ESP the surging.

Sorry to be a dummy but there is no pull-out choke (at least not on the dash). Just a throttle lever, which as I understand it, when pushed all the way forward it is "choked" then below that is the Bunny and the Turtle, which controls the running speed between "fast" and "slow".

This tractor will never tolerate "choke" once the engine turns over. Backfiring definitely worse at slow than at fast.

Am going out now to try the Sea Foam.

 

[1010]

got yah! I didn't think about the choke being wide open throttle,