Bad gas?

[GirlWhoWantsTractor]

Just had complete service done by Husq mechanic.

Engine surges and gives explosive bangs when idling or driving, but not when mowing. Then when I stop it, turn the idle down before turning it off, the explosions get louder. After the engine cuts off, it gives one final very loud bang like a gunshot.

This will be an easy one for you guys....I hope.

 

[Thomas]

How old the gas?
Twin cylinder?
Chock fully off?
Notice any oil leaking from motor head?

 

[GirlWhoWantsTractor]

How old the gas?
Twin cylinder?
Chock fully off?
Notice any oil leaking from motor head?

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.

 

[joecoin]

Make certain your spark plug is tightly seated .

 

[GirlWhoWantsTractor]

Make certain your spark plug is tightly seated .

Will check that in the morning. Thanks.

With all this backfiring, will the plug likely be fouled?

 

[tomplum]

To start with the fuel should be changed out, but it sounds like an idle air bleed issue with the carburetor. The newer 1 barrel carburetors seem to have issue with that. You could contact the service person and have them recheck. It is possibly not something covered in normal preventive maintenance, but if it was running poorly- they could have at least talked to you about it. In regards to after fire: When you turn off your ignition switch, there is unspent fuel in the intake manifold and combustion chambers which ignites due to the heat. There is an anti-backfire solenoid at the base of the carburetor which closes at that instant the switch is turned off. It is there to prevent more fuel from being pulled from the bowl of the carburetor. That is how this happens. You can verify that the solenoid is working by detecting a click at the solenoid when the key is cycled between off and on.

 

[dragoneggs]

Still reeling a bit from eating BBQ and Mexican this evening. I thought I might be able to contribute to this thread. Sorry.

 

[GirlWhoWantsTractor]

It's been constant problems with this tractor, in case you haven't seen any of my other posts about it.....

Thing is, it's usually running fine when first dropped off after service or fixing, at least for a short time, like for a couple of hours. Then, another problem arises, not always the same one.

I've lost track over the months but remember distinctly the first week I had this bran' new tractor, the motor clutch dropped out. Two starter switches, battery failed, blade assembly fell apart, etc., etc. IDK at this point I've forgotten all the stuff they've replaced. I should gather my tickets and receipts.

The most recent history: a few months ago it refused to start, no click even, but (new) battery showing strong. So they took the tractor in for a couple of weeks, and thought they'd fixed it. Dropped it off then it wouldn't start again. They took it back, kept it another few weeks, replaced the main motor clutch (again), said they were calling in a priest for an exorcism ( ). They finally replaced entire electrical system, and dropped it off like a week ago. Now after a couple of hours of mowing, this backfiring.

Was hoping maybe this time it was just bad gas....not yet another major issue.

 

[Wagtail]

By the sound of things (history and present problems) it appears that you have a genuine HOYT-CLAGWELL tractor.

A rare make/model of tractor indeed.

 

[GirlWhoWantsTractor]

By the sound of things (history and present problems) it appears that you have a genuine HOYT-CLAGWELL tractor.

A rare make/model of tractor indeed.

hahahaha

 

[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,