Hi. In September 2017 I bought a Craftsman branded Husqvara lawn tractor with a Briggs and Statton 24hp Platinum Intek 2-cylinger engine. Last time I used it was in December to pick up leaves and during that time is started hunting and surging when the engine was not under some kind of load - either moving or blade engaged. I though it might be temperature (it was in the 20s) and moved the throttle to the cold air position. I brought it out of my shed for the first time yesterday and the problem persists (its now in the 50s). I always use fresh gas with ethanol treatment additive. The air filter and gas filter are still new. I've got about 7 hours on it right now. I've got an on-site service warranty on it but if it is something simple I'd rather adjust it myself.

Is this hunting and surging issue on a relatively new engine usually the governor? If not, what else might i look for or try before I call in and schdule a service appointment?

Thanks.

I would use some Sea Foam to clean the carb jets.

Walmart usually has the best price.

More than likely you have a piece of crap partially blocking the main jet.

Seems to be typical of this model. Try leaving the choke out for a while until the engine warms fully. That works for me. Don’t like running with choke partially eng@ged for so long but that seems to be what this engine likes.

I'm running sea foam through it now. I may try adjusting the governor if that doesn't work.

Or you could try cleaning the main jet like shifferbrains suggested. If you don't know how to do that, you probably shouldn't try adjusting anything. Just call the service people instead.

Also dump the old fuel and get some new fuel. Especially not ethanol. Get recreational vehicle gas. It’s ethanol free and about 89 octane. Ethanol fuel is only good for a month or two, then l get the same symptoms. Try it

This message has been edited. Last edited by: greco,

quote:

Originally posted by trapper189:
Or you could try cleaning the main jet like shifferbrains suggested. If you don't know how to do that, you probably shouldn't try adjusting anything. Just call the service people instead.

Why tear it apart when Sea Foam gremlins go inside and scrub away.

Even if you use stabilizers, ethanol can still plug things up over time if it has been setting.

I had the fuel line completely plugged on one of my lawn tractors which was too much for Sea Foam.

24HP size may be a stretch, but the air-controlled governor is where I first look on a B&S that is surging, I've found leaves, a t-shirt/rag, even an old wasp's nest inhibiting free movement of the governor vane. As implied above, I doubt they would be so cheap as to use this type of governor on a 24HP engine, but it is easy to diagnose and fix, and this kind of thing can affect any mechanical governor.

quote:

Originally posted by 41:
Why tear it apart when Sea Foam gremlins go inside and scrub away.

Even if you you stabilizers, ethanol can still plug things up over time if it has been setting.

I had the fuel line completely plugged on one of my lawn tractors which was too much for Sea Foam.

I know, right? I wish Seafoam worked anytime I've tried it. On many small engines the main jet is fairly easy to get at. You pull the float bowl, there it is, and you don't even have to pull the carb off the engine.

I had a carb on a Yamaha ATV that I ran Seafoam through. Didn't work. Tore the carb apart and it was a mess. Cleaned everything, put back together and it ran better, but not right. I broke down, bought a rebuild kit, compared the new to old parts and I couldn't see a difference. Installed the new parts and it runs like a champ.

Another classic was the needles on my FJ1200. They had stuff literally growing on them. I cleaned them, but they were pitted and I had to replace them.

I've stopped using ethanol in any carberated engine. I've had too many issues with it. I also don't mess with Seafoam anymore. Chances are if something in a carb is so clogged that gas doesn't flow, Seafoam won't flow through it either.

quote:

Originally posted by 41:

Even if you use stabilizers, ethanol can still plug things up over time if it has been setting.

It hasn't been sitting. I bought it in September and used is several times until December. Only on the last use in December did it do this. Not too bad, though. Before putting it away for the winter I disconnected the fule line and ran the gas out of the engine unti it cut off. I started it again yesterday and it seeemd to start doing it again where it left off.

In my experience, new engines sometimes need retuning of the carb after break in. I have no idea of the particulars with that engine though.

This PDF might help: B&S Carb Troubleshooting Guide

Failure Table #12
Hunting & Surging
•Jet, Main Fuel
•Restricted, Passage
•Jet, Pilot
•Governor

I will schedule a service call.

I took the aifilter out and sprayed in carb cleaner. No effect.

I turned it off and poured a bit of raw sea foam into the carb. It blew a little white smoke but never stopped surging.

I poured a bit more in, ran for a couple of seconds then let sit for awhile. Restarted, blew out some white smoke, and after the sea foam cleared it still surges.

Loosened the governor locking nut and tried to turn the governor shaft to the right but its all the way over.

I adjusted the idle speed screw thinking it may be out too far but its set correctly.

I can only assume its a jet at this point. Not a big deal but since I have free on-site service for another 6 months, I'm going to avail myself of that.

Thanks everyone.

You need to put it in the gas. Pouring it into the carb will not pass through the jets! Have another beer and try again tomorrow.

Also it is dangerous to pour it into the carb and could cause a fire.

I would take the gas out of the tank and run a 1 to 4 ratio of Sea Foam to gas. So 8 ounces of Sea Foam to a quart of gas. If that does not solve the problem, you probably have some dirt in the carb blocking the metering to the jet.