Small Engine Question

[Boz330]

I have a Landmaster UTV with a 16HP Briggs Vanguard engine. Lately it has been surging at low speeds. It didn't use to do that. I use this thing around the farm for spraying, seeding and fertilizing which is all done at slower speeds. Does anyone have any ideas on how to correct this. I think it could be related to the governor but I've never messed with small engines much.

Thanks
Bob

[tomme boy]

What kind of gas are you running? Ethanol in not very friendly to carbureted engines. You might have a little water in the gas too.

[Beagle333]

Surging is usually caused by running too lean. Check the plug and make sure it is good and firing hot, then check fuel lines and filters to make sure not clogged or possibly cracked and sucking air somewhere. If that is all good, then you can start adjusting the screws on the carb to give it more fuel. Often times I have seen this caused by a cracked/dry-rotted fuel line letting air in.

[WILCO]

I think it could be related to the governor but I've never messed with small engines much.

Hi Bob!

Take it to a qualified small engine mechanic.
I did after I screwed things up.

[country gent]

I have found on alot of small engines that sit alot gas goes bad in time and dosnt run as good. I use a small amount of Stabill in the fuel on them. Could be a build up of varnish in the fuel system try sefoam additive in the gas just a ounce or so should do it there.

[rockrat]

Sounds like your low speed jet is getting clogged up. First thing I would try is cleaning out the gas tank and filling it with non-alcohol gas, if you can find it. Use Techron injector cleaner at about double/triple strength. You might be able to get the low speed jet unclogged that way. Try changing plugs along with the clean fuel.

[docone31]

I had that happen on my tiller. Clean out the carb, water and debris collects in the bowl and plugs the jets.

[lancem]

Surging is usually caused by running too lean. Check the plug and make sure it is good and firing hot, then check fuel lines and filters to make sure not clogged or possibly cracked and sucking air somewhere. If that is all good, then you can start adjusting the screws on the carb to give it more fuel. Often times I have seen this caused by a cracked/dry-rotted fuel line letting air in.

Agree with Beagle, my experience has been with most of the newer engines I've had that they have them set up lean to begin with to meet pollution specs at the factory and once they break in good then they are way too lean and the surging begins. Most now have a plastic cap on the adjustment screw to prevent it being adjusted much and you have to break it off to get full range of adjustment.

[Boz330]

Thanks for the suggestions. The UTV just turned a year old so I went through the recommended maintenance for a year. Didn't notice any deterioration of the fuel hose but I will look closer and swap out the fuel filter. I did try partially choking the engine to see if that helped and there was no noticeable difference. I did notice the plastic cap and wondered what it was. I normally add a little B-12 carb cleaner about every other tank or so.
I can get non-alcohol gas but it is 70 cents more a gallon. Total time on this engine is 84hrs and it has all been alcohol gas. Normal stations around here only carry the alcohol gas. There is one station that carries the non-alcohol gas and caters to the local pilots that have approval to use that gas in their airplanes. The guy I fly for uses a mix of avgas and non-alcohol and I thought about trying that but that still puts the cost at $5+ a gallon and this thing isn't exactly a gas sipper.

Bob

[R.M.]

Check to see that the carb mounting bolt have come loose. While it's running, spray some WD40 around the base. If engine speed changes, you are sucking air. The gasket could be shot, or the carb loose.

[oneokie]

Also check with local marinas that sell gas.

[KAF]

I used some mechanic in a bottle, and add ethanol shield to every can of gas I buy. I buy 15 gals at a time add the stabilizer and it will be fine after all winter and most of the spring.
http://www.b3cfuel.com/products/ethanol-shield/

[oldred]

I work on a lot of farming and lawn equipment and I see a lot of a SERIOUS problem with Briggs engines in that HP range, it can and will destroy your engine if it is indeed the problem! What it is that I see often is the screws that holds the butterfly in the carburetor works lose allowing the butterfly to flop back and forth causing the surge but the real problem occurs when one of the screws falls completely out and gets sucked into the engine where it will immediately destroy not only the top of the piston but usually the cylinder head and sometimes even the cylinder walls too. I am not saying for sure this is your problem and most service centers will deny this is a problem but believe me when I tell you that no matter how much they deny it they know full well it's true, I have see four of these things just in the last couple of years!


Remove the breather tube and any parts that block your view of the carburetor intake, make SURE the screws securing the butterfly are tight! If they are tight then you have another problem of which there are several that can cause this BUT make sure those screws tight before running your engine anymore. Briggs must be aware of this but still they went for several years before doing anything about it and literally thousands of engines have been ruined because of it.

[Boz330]

Good to know, I'll check that this evening.

Bob

[MaryB]

Now I need to take the shroud off my lawn mower and make sure those screws are tight... 21hp Briggs Platinum engine.

[doc1876]

all small engine repair guys I have talked with say run premium in them unless you can get the good additives.

[oldred]

Running premium is a waste of money in these engines since the compression ratio is so low spark knock is almost unheard of even with the higher operating temperature. However on a two cycle engine using premium and also 100% gasoline vs the alcohol cut stuff that's so common has some advantage but on the four stroke even the 100% gas does not matter much, the exception being the "four mix" engines such as the Sthil mist lubed that are basically a four stroke that uses a 50:1 mix just like a two stroke. Using premium in any engine that uses a fuel/oil mix is a very good idea but this is because of the oil in the mix and not for the normal reasons premium is used in a gasoline engine. Even though some conventional four stroke engine manufactures suggest premium fuel, most simply suggest high quality fuel, when asked they will tell you that any normal grade of fuel sold in the U.S. is ok. These engines are sold all over the world and a lot of countries have some very questionable fuel grades so suggesting premium is the prudent thing to do, here in the U.S. regular grades are all that's necessary however.


Premium gasoline is probably the most oversold and hyped product in history! People pull up to the pump and pay 40 to 50 cents or even more per gallon thinking it's better for their engines and/or that they get better mileage from the stuff but actually they are simply wasting money! Unless an engine is designed to need premium (it will be labeled at the filler cap and/or fuel gauge and always in the owner's manual) paying money for higher octane is just blowing money out the tail pipe! The only meaningful difference between regular and premium is the octane rating (sufficient levels of detergents are now required by the Government in all grades) and all the octane increase of premium does is to lower the detonation point (the mixture burns slower) so that higher performance (high compression, turbo or super charged) engines will not suffer from spark knock. Engines designed to run on lower octane fuel (by far most of them) DO NOT get better fuel economy from higher octane and the octane rating does not mean it makes more HP.


The oil companies have done a fantastic job of overselling this fuel over the years, just look next time you pull up to the pumps. You are constantly bombarded with ads at the pump hawking their premium fuel, catch lines like "feel the power" or "increased mileage" but more power or better mileage than what? NEVER EVER will you see claims of better power or mileage than regular grades because it's not true and they couldn't get away with it -like they do now!

Sorry for the fuel rant but this one is a pet peeve of mine.

[6bg6ga]

Never run any gas that has alcohol in it. When your done checking the mounting bolts and the jet adjustment don't forget to pull the air filter and either clean it or replace it.

[oldred]

Never run any gas that has alcohol in it.

While that's good advice it may be very difficult for some folks to follow since 100% gasoline can be VERY hard to come by in some areas!

On a four stroke it's not nearly as important as the two stroke engines (and the also the "four mix designs") because of the way they are lubed. However anytime alcohol can be avoided it's usually a good idea since it can have adverse effects on not only seals and gaskets but it can actually damage aluminum parts especially in the carburetor. Older engines have a bigger problem with this than the ones built in the last twenty years or so but still it's a good idea to stay at or below a 10% mix if 100% is not available, actually 10% or less is not likely to cause any harm.

[Mallard57]

I would say start with draining your fuel bowl of sediment.
Jeff