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

[Frank46]

I have a two year old sears riding mower think its a 24 hp B&S engine. Running really bad and called sears as it is still under warranty. Guy shows up and tried to start it and no go. replaced the carb and now it's running fine. He did ask what gas I was using and told him mid level pump gas with the 10% alcohol. Frank

[6bg6ga]

Ok, probably 20 years or so ago the alcohol was causing problems with aluminum in the fuel systems and yes todays cars have been engineered to withstand the use of alcohol in the fuel. Unfortunately until recently the small engine manufacturers have just started jumping on the bandwagon with parts that can withstand the 10% blend. So, it does depend on the year of manufacture as to if the engine can take the blend. Generally it is a very good idea to use 100 gasoline without the 10% blended into it. In the midwest its still common to obtain 100% gas just look for the no alcohol label on the pump.

When in doubt check your owners manual to see if your small engine is rated to use the blend but its a good idea to simply steer clear of it even if you have to drive an extra 30 miles to purchase non alcohol gas.

[oldred]

The problems become more common when the mix is above 10% by even a small amount and this can easily be exceeded by some of the additives some folks use. READ THOSE LABELS! Some additives can cause more harm than good! Some of those products are little more than alcohol (often listed as ETOH) and a couple of other chemicals such as Naptha and/or Toulene and these can actually do far more harm than good in a small air cooled engine. When used properly they are usually safe enough, although most don't do much if any good either, but the main problem arises when too much is used in a small gas container. This stuff is meant to be used in a car or truck with at least 8 gallons or more of gasoline in the tank but lots of folks will simply dump a bottle in a five gallon container or less where it does not get diluted nearly enough, this when combined with alcohol already in the pump gas can lead to problems. I have known of people dumping several bottles of this junk (and that's what most of it is!) into their vehicle tanks in an effort to solve an engine running issue without stopping to think what it might be doing to the system, the attitude seems to be that if it calls for 1 oz per gallon 2 oz will work so much better I think I will use 3 oz! In most cases the additives do little if any good, some injector cleaners MIGHT help dissolve residue from poor quality gasoline but simply switching dealers and using quality fuel will work better. The cleaners do nothing however for an injector clogged by debris and rarely do any more than the cleaning agents already in quality gasolines, a certain level of which is required by federal law.

If there is anything fuel related that is oversold and over hyped more than premium fuel it's fuel additives! Used properly they most likely won't do any harm but most of what they are supposed to do is already done by use of quality fuel and adding more simply doesn't help while adding too much can do harm. The one exception is for removing moisture from the fuel and preventing freeze up in really cold weather, these additives contain a chemical that will absorb water in the fuel both allowing it to mix with the gasoline and end up going out the tail pipe as water vapor and acting as an antifreeze to any water still in the fuel system, what is this chemical? ALCOHOL! The same stuff that is added to gasoline at the pump is also sold as an additive in little plastic bottles at Wally World and your favorite auto parts store at grossly inflated prices with wild claims of almost magical cures for all of your engine woes!

[rockrat]

Unfortunately, around here , 91 octane is the only 100% gas I can find. Got tired of taking ATV's in every spring to get the carb cleaned because of the alcohol fuel. Mechanic (owner/bike racer too) told me to use non-alcohol gas. would cost him money buy not working on the ATV's every year, but will help a bunch. I know the ATV's and lawn mowers are easier to start with the 100% gas. Might cost me $20 more a year to run the stuff, but will save about $150 a year if I don't have problems because of the alcohol fuel, in decreased maintenance bills.

Oldred, I agree, the octane pushers are just pushing a bunch of hype. Mainly because they make so much more money off of the higher octane fuel than they do they regular fuel. I heard it was only 8 cents cost between regular and premium, to make, but usually around here the stations charge 30-35 cents more for premium. You can get better mileage from lower octane fuels because of the longer hydrocarbon chains and the energy in the molecular bonds.
Now, if your engine is designed to work with higher octane fuels, you might do better with premium. I get better mileage with the lower octane fuels in my pickup, but the kid gets alot better mileage , in their car, with premium, more than enough to make up the difference in cost. The wifes car likes mid grade, for best performance/mileage, but the extra cost isn't worth it for the results. Each car/driving style can be different.

[Finster101]

Higher octane is simply slower burning to prevent knock in higher compression engines. It work well in air cooled engines in high heat situations like motorcycles in traffic. I do prefer non alcohol fuel for my lawn equipment, for one thing it seems to store better. I'm a car guy, sounds like Oldred is the go to guy on small engines.

[oldred]

That's the kicker, some folks waste a ton of money on premium fuel thinking they are getting better mileage when in fact just the opposite is true! In an engine designed for regular grades, or any engine that is not experiencing spark knock with that fuel, slightly better fuel economy is obtained with regular for two reasons. First the flame propagation is faster leading to more efficiency (as long as the detonation point is not reached) and the extra additives in the premium means that there is actually less actual gasoline per gallon volume. These additives, while they do burn, do not produce near the energy of gasoline thus the more gasoline displaced by additives the less high energy fuel available per gallon volume. Of course any mileage loss due to the additive displacement of true gasoline is going to be fairly insignificant and is more or less just a case of "nit picking" but it still amounts to additional loss no matter how small vs the gain that some folks mistakenly think they get. The bigger difference however is the slower burn rate which does translate to a small decrease in power and mileage in these low compression engines designed for regular grades, for these reasons so called racing fuel would lead to an even bigger loss of power and economy in these engines!

So why does premium make so much more power in engines designed for it? The short answer is it doesn't! What it does do is ALLOW the ENGINE itself to make more power by being built to a higher much more efficient state of tune, more compression, earlier ignition timing, modified valve events, etc. This allows the engine to burn the fuel more efficiently thus producing more power per pound of fuel which translates to more power, this kind of performance can not be obtained by using lower octane fuels however because the detonation point of the fuel/air mix would be to low. The manufacturers strike a balance between power and over-all efficiency based on what the vehicle is meant to do thus a hotrod Mustang GT is going to require high octane fuel while a common grocery getter will only need regular grades. These lower performance engines can burn either fuel without reaching the detonation point and paying extra money for a higher octane fuel that does nothing except to raise the detonation point even higher than the engine needs is simply wasting money, still lots of folks seem to think that the premium must be somehow better because it costs more!



Then there are the folks who do indeed to seem to solve a problem by switching to the higher grades of fuel but have they done the right thing? Before I retired I heard it all the time, "I can hear my "valves rattling" if I burn regular" but not with premium, so have they solved a problem by using premium fuel? In a way yes but they are going about it wrong, first off although it's a common thing to have someone think they have "valves ratting" (I bet I have heard that a thousand times!) what they are actually hearing is spark knock or detonation in the combustion chamber, you will not hear a valve "rattling" unless there is a SERIOUS mechanical problem such as a broken valve spring and switching gas is not going to fix that. That rattling sound is when the gas/air mix ceases to burn in a controllable manner with smooth flame propagation but rather detonates almost instantly creating a shock wave that smashes down onto the piston rather than a smooth downward push, many things can cause this. If the engine is designed for regular grades of gasoline and spark knock is encountered with that fuel then switching to a higher grade or using an octane booster may very well seem to solve the problem BUT it's more than likely it would be much cheaper and better for engine life in the long run to repair the cause of this detonation rather than mask it with more expensive fuel! Ignition timing, worn timing chains, carbon build-up from a faulty EGR system (very common cause), vacuum leaks, various sensors being out of calibration or completely failed, etc all can cause this problem and masking the symptoms by buying a more expensive fuel then most likely using even more of it due to the mechanical fault being hidden simply makes little economic sense, at least to me anyway.

[KAF]

Higher octane gasoline contains MORE alcohol per gallon. That is what makes it run cooler and prevent preignition, the "knock"

[Finster101]

Higher octane gasoline contains MORE alcohol per gallon. That is what makes it run cooler and prevent preignition, the "knock"

Some does not all. On a different note, the supercharged guys can do some wicked things with E-85.

[oldred]

Well actually most premium fuels contain more than just alcohol to raise the octane rating, chemicals such as toluene, heptane, etc are used in varying amounts by the manufacturers but you're right alcohol is used also in some formulations.

Folks who think they are getting better mileage and their money's worth by buying premium for their cars that don't need it may be mistaken but those who think they get better mileage from 100% gasoline vs "gasohol" are right! Alcohol and gasoline mix in whatever percentage vs 100% gasoline is another mileage consideration when buying fuel that's completely separate from the regular vs premium discussion. It can flat out be said that "gasohol" gets poorer mileage than 100% gasoline and the difference can be significant! Regardless whether it's mixed in regular or premium alcohol simply does have the BTUs per pound as gasoline, alcohol will produce roughly 50% less power per gallon of fuel vs 100% gasoline thus if even 10% of a gallon of fuel mix is producing 50% less power than the amount of gasoline it is replacing the loss of mileage can become significant. That nickle a gallon saved at the convenience store "gasohol" pump vs the 100% "name brand" across the street might not be such a bargain after all!

[oldred]

the supercharged guys can do some wicked things with E-85.


They can indeed, to the point of almost being mind boggling! It's due to an extension of the same reasons that premium is used in high performance gasoline only engines. Alcohol powered race car engines can be made to make gobs of power because of the extremely high detonation point of the alcohol fuel, there is much less power per pound of fuel in alcohol vs gasoline but the engines can burn a LOT more of it per cylinder charge resulting in huge net gains of power. Everyday street vehicles can be made to run on pure alcohol but mileage is very poor vs gasoline as those flex fuel owners who ran E85 found out. Those flex fuel engines were a major compromise anyway in an attempt to be able to run either fuel, while things such as ignition timing and fuel mixture can be computer controlled to allow fairly efficient use of high alcohol percentages other things like the compression ratio can not, a high alcohol ratio needs that higher compression ratio to more efficient. When combined with a supercharger the aforementioned awesome performance can be obtained using relatively low compression ratios but it does so by forcing copious amounts of fuel/air mixture into the cylinder, this results in impressive power but not so impressive fuel economy!

[wallenba]

If that engine has a rubber or synthetic priming bulb, they can develop leaks. Not fuel, but air. Excess air entering after the carb will thin the mixture resulting in surging.

[oldred]

My apologies for getting so far off-topic, I just realized I was getting a bit carried away there, I will hush up now! :oops:

[mack1]

In two diffrent small engines I have had a plastic puddy like substance form in the lowest part of the fuel system with fuel in it. First it was the jet in the fuel bowel the next time it was the sump in the tank because I turned the gas off and ran the bowl dry. I think letting e10 set for to long caused the problem. I no longer will let alcohol fuel set for more than a month or two in anything.

[MaryB]

All you can get in MN is E10(and now e15 in some places), along with E85. No alcohol gas is at some boat docks but nothing close to me. So all my small engines run the 10%, I just make sure to run the carb dry the end of the season. Only had 1 problem and that was on my 20 year old snowblower, The alcohol ate the fuel line and gummed up the carb bad. It was using a LOT of oil too so I sold it as parts and replaced it.

[rockrat]

Correct me if I am wrong, but don't most hydrocarbon have about the same amount of BTU's/lb. So a pound of alcohol has the same BTU's of , say, gasoline. Its just that alcohol has a lower weight per gallon than gasoline does, therfore it takes more alcohol to make the same power. So air/fuel ratios need to be lower.

[oldred]

Alcohol has substantially less energy per gallon and per pound than gasoline, I knew it was around 40% less but I didn't know the exact numbers so I asked Mr Google for the actual figures.

Gasoline has 114,000 +/- to 116,000 +/- BTU/gallon (depending on whether it's a summer or winter formulation) vs 76,330 BTU/gal for straight alcohol.

Alcohol weighs 6.58 lbs

Gasoline weighs 6.2 to 6.3 pounds/gallon depending on the formulation

[6bg6ga]

Some does not all. On a different note, the supercharged guys can do some wicked things with E-85.

If you have a piggyback computer system like FAST then its possible to use E85 when running on the strip with a supercharger.

Its popular with turbocharger guys because they program the fuel system to dump a bunch of extra fuel into the engine and the unburned fuel helps to spool up the turbo turbos and make boost just sitting there on the line. That in conjunction with the stutter box and line lock and transbrake allow the car to be at near max boost if needed when they leave the line. Keep in mind there is probably an additional controller which actually controls the amount of boost.

With my supercharged car I will not touch E10,E15, or E85 and dispite the fact that I lowered the compression the additional boost actually raises compression to the point that a spark retard box has to be adjusted in order to maintain a condition of no knock. In addition no platinum spark plugs are generally used in a non-factory turbo or supercharger engine because they can cause detination.

Now, I have seen some small engines that need to stay away from E10,E15,And E85 fuel simply because of their high compression. Alcohol and high compression engines not designed for alcohol is a no no in my opinion. I had a Johnson 235hp outboard on a Hydrostream V-King low profile high performance boat that required premium fuel only. The engines manual stated premium fuel and I was always looking for a additive for the fuel to boost the octain and slow down the burn rate like premium fuel does. I finally got rid of the boat because it was too much hassle to find decent fuel.

My company Ford E250 van delivers more mileage with non-alcohol gas than it does E10 or E15. I've kept track of the mileage at every fill up and I loose about 1.5-1.8 mi per gallon using the E10.

[Finster101]

With all this side track discussion (we got to have a little fun) I wonder did Boz find his problem?

[6bg6ga]

The side track info is always useful in my opinion and it contributes to discussion. Hopefully others will join in.

[oldred]

If you have a piggyback computer system like FAST then its possible to use E85 when running on the strip with a supercharger.

Its popular with turbocharger guys because they program the fuel system to dump a bunch of extra fuel into the engine and the unburned fuel helps to spool up the turbo turbos and make boost just sitting there on the line. That in conjunction with the stutter box and line lock and transbrake allow the car to be at near max boost if needed when they leave the line. Keep in mind there is probably an additional controller which actually controls the amount of boost.

With my supercharged car I will not touch E10,E15, or E85 and dispite the fact that I lowered the compression the additional boost actually raises compression to the point that a spark retard box has to be adjusted in order to maintain a condition of no knock. In addition no platinum spark plugs are generally used in a non-factory turbo or supercharger engine because they can cause detination.

Now, I have seen some small engines that need to stay away from E10,E15,And E85 fuel simply because of their high compression. Alcohol and high compression engines not designed for alcohol is a no no in my opinion. I had a Johnson 235hp outboard on a Hydrostream V-King low profile high performance boat that required premium fuel only. The engines manual stated premium fuel and I was always looking for a additive for the fuel to boost the octain and slow down the burn rate like premium fuel does. I finally got rid of the boat because it was too much hassle to find decent fuel.

My company Ford E250 van delivers more mileage with non-alcohol gas than it does E10 or E15. I've kept track of the mileage at every fill up and I loose about 1.5-1.8 mi per gallon using the E10.



It sure has come a long way since my drag racing days (late 60's and early 70's), in those days it was cubic inches and a couple of Holly double pumpers for high tech!

[oldred]

To get back on topic let's take a look at small gasoline engines of the type used on lawn mowers, lawn tractors and other four stroke around-the-home type of equipment. High performance small engines used on motorcycles, some ATVs, boats etc are in a different class and each need to follow the manufacturers recommendations.

There have been a couple of instances here where someone was asked by a service person what kind of fuel they were using when discussing a running issue but let's look at that. By far most operational issues with the small engines involve fuel delivery to the intake, clogged carburetors and strainers being the most common but that's a fuel QUALITY issue not a matter of premium vs regular. Alcohol in the fuel can cause problems due to the fact it degrades certain gaskets and seals and in the case of older models it can even soften rubber fuel lines to the point of leakage and having residue from the softened rubber clog the carburetor, it can even attack aluminum parts causing a powder like residue to form which can also cause clogging. None of these problems are due to premium vs regular but "gasohol" vs 100% gasoline is a whole different story! The bottom line is to keep these engines happy buy quality gasolines, 100% when possible and no more than a 10% mix, and keep it CLEAN! By far most problems I saw was due to contaminates in the fuel, most times it was simply water, from poor storage and failure to prevent dirt, water and other debris from entering the tank. Improper fuel containers also account for a lot of problems, plastic jugs such as milk and water jugs are often used for gasoline storage but they are not only illegal for this they degrade and can release a stringy like residue that can clog the carburetor and fuel strainers/filters. However probably the most common fuel related failure is due to old fuel! Gasoline has a relatively short shelf life and will degrade rather quickly leaving a shellac like substance in the carburetor that can be very difficult to remove, in some cases it's nearly impossible to get it all out of those tiny passages. Carburetor cleaners (the spray type) are useless for cleaning a clogged system and all they will do is clean the gunk off the outside and the throat of the intake which is almost always clean anyway, it does absolutely nothing for a clogged carburetor unless the thing is totally disassembled then it can be used to dissolve the gunk on individual parts.

Buy clean good quality fuel, keep it clean by storing it in clean approved containers and store these in a cool area out of direct sunlight. A container of gasoline sitting in direct sunlight on a hot day can degrade in a VERY short time because it evaporate rapidly when heated and all of the chemicals do not evaporate at the same rate! Don't let an engine sit more than a month with fuel in the carburetor unless a fuel stabilizer is added (Stal-Bil brand is really good), any longer than that and the engine should be run until it stops from fuel starvation before storage.

Just a note on fuel stabilizers, follow the mixing directions to the letter and do not add even a small amount more than it calls for, this is one case where more is definitely not better! Even a small amount too much will result in gasoline that will not burn properly and the engine will run poorly IF it can even be started! Adding too much will not cause serious harm but can easily result in the need to drain the entire fuel system and replace with fresh fuel.


As for the premium vs regular in these engines premium simply is not necessary, it won't hurt anything but it's still a complete waste of money and I have never seen any running issues due to using regular fuel -poor quality fuel yes but never from a lack of octane. Millions of these engines run on regular everyday without issue and it's easy to see why when one looks at the design, most have about a 6 to one compression ratio and that would have to be above 9 to one even in a hotter running air cooled engine in order for detonation to occur. If the engine failed due to using regular vs premium it would be a major failure and not simply a running issue, the only difference between the higher octane premium and the regular fuel is a higher detonation threshold and if that occurs the engine will literally beat itself to death! What too low octane damage would look like would be severe piston damage and/or burned exhaust valves if heavy detonation occurs while lesser intermittent detonation can also cause piston damage it usually results in accelerated connecting rod wrist pin and crank bearing damage from the pounding. I have yet to ever see any of this occur in any of the engines of the type the OP was discussing, the way they are designed there simply is no reason for it to happen. I have seen a lot of these engines fail due to overheating, dirty oil, no oil, improper oil and from the engine ingesting dirt and foreign objects into the intake. The only problems I have ever seen or even heard of that involve fuel is either fuel that will not burn properly due to age or contamination or simply a clogged fuel system and all of these problems are just as likely to occur with premium as with regular.

[dubber123]

oldred has much more experience with this issue than me, however I would suggest if in doubt with your particular vehicle/equiptment combo, try the different octane fuels and keep notes. I have owned vehicles that according to the manufacturer needed only regular fuels, but showed better performance and economy when using a higher octane. My and a friends mid 90's Toyota cars were an example. Running mid to high octane more than paid for itself, and I didn't have to listen to detonation pulling hills. My current Subaru doesn't rattle on mid grade, but will on regular, as did my girlfriends last Subaru. My 1953 Dodge M-37 runs noticeably better on regular than it does on the higher grades. Of course it has a dash tag that reads "minimum octane 68".. :)

[oldred]

Just a quick quote from a Consumer notice from the Federal Trade commission, (extra emphasis on certain phrases is mine but it's worded exactly like they published it)

"In most cases using a higher octane gasoline than your owner's manual recommends offers ABSOLUTELY NO BENEFIT. It won't make your car go faster, GET BETTER MILEAGE or run cleaner."

That quote is from a consumer notice from the Federal Trade Commission.






If your engine is designed for regular (have you checked the owners manual?) and that's what the manufacturer recommends then it's quite likely that you have other issues causing the spark knock, or "rattling", and premium only masks these issues. It's usually cheaper and better in the long run to correct the cause rather than mask it with more expensive fuel, there is absolutely nothing in premium fuel that can make more power per gallon to give you better mileage and in fact for the two reasons listed earlier it will actually result in slightly less (although probably by an insignificant amount) fuel mileage on a properly tuned regular fuel engine. If the premium fuel eliminates "knocking" then it can result in better fuel mileage vs an engine running in a "knocking" condition but in almost all cases this will constitute only a small percentage of the time the engine is running, such as a heavy load during acceleration or lugging on a hill. At all other times there would be zero difference between premium and regular, at times the engine was not "knocking" or "pinging" on the regular it simply makes no difference at all except to your wallet. If the engine is meant for regular and you have to use premium to prevent "knock" at all times then you have far more than just a fuel choice issue, in any case it's nearly impossible to overcome the price difference even in an engine that "knocks" on occasion using regular.


At 20 MPG and 20,000 miles driven per year a price difference of .40 per gallon (that what it is where I buy most of my gas) adds up to $400 dollars per year to use or $2000 extra to put 100,000 miles on the odometer with premium vs regular! When compared to all the other vehicles of the same make who drive the same distances without damaging their engines on regular it gets kind of hard to justify those costs. Again there is absolutely nothing in premium gas vs regular that will increase power and fuel mileage in an engine that is not suffering spark knock and even then it only helps during the load situations where the knock is occurring! The fuel companies have done an excellent job of misleading the public, and why wouldn't they it's making MILLIONS of dollars for them, but NOWHERE will you find information from them that will make any claims of better mileage from premium vs regular! What you will find is advertising hype saying things like "better performance from super premium", but better performance than what? NEVER, EVER will they say better performance vs regular or anything else, they will NEVER say what this "better performance" is related to! It's nothing but a slick word game and if there was even the slightest fuel mileage gain to be realized from premium vs regular they would jump all over it because it would be a gold mine for them and they would be plastering it all over their ads instead of just the vague references but you never see them do that, wonder why that is????

Here's what the experts have to say about it and there are many clear explanations of why better mileage from premium is just an illusion, this has become true even for some newer cars that have a premium fuel recommendation. The switch will result in only a slight power loss under load such as acceleration for passing or pulling up a hill, at other times the computer monitors driving conditions and nothing is lost or gained. That is for some newer cars that recommend premium, for older cars that recommend regular there is little or no difference one way or the other.


(The above is for cars that RECOMMEND premium, most high performance and turbo/super charged engines REQUIRE premium and there is a big difference there! If the manual and labels on the fuel gauge/fuel filler say REQUIRED instead of RECOMMEND then the engine should never be run with regular)


This link is a really good assessment but you may have to click the "re-direction" link from the first page, it's a really good read! http://www.businessinsider.com/using-premium-gas-often-a-waste-of-money-2013-8

A few more,

http://www.consumerenergycenter.org/transportation/consumer_tips/regular_vs_premium.html

http://blog.truecar.com/2011/03/03/premium-vs-regular-gas/

http://usatoday30.usatoday.com/money/autos/2003-07-30-premiumgas_x.htm

http://www.cbsnews.com/news/6-myths-about-gas-mileage/




And there are literally hundreds more explaining why it's impossible for premium fuel to deliver better mileage than regular no matter what some have come to believe. The bottom line is that premium and regular are the same thing with the only difference being the additives in premium to raise the detonation threshold, there is NOTHING in premium that will make it produce more power or increase fuel mileage!

[Boz330]

With all this side track discussion (we got to have a little fun) I wonder did Boz find his problem?

No he didn't. The engine is one year old with 85hours on it. I had to pull the top off of the carb to check the screw in the throttle plate as oldred suggested. The inside of the carburetor was clean as a pin and the screw was tight. There were no adjustments on the exterior of the carb except for a stop screw for the throttle. The fuel filter is clear and looked clean. All hoses were in good shape.
The UTV gets driven several times a week so gas doesn't sit too long in it since the tank only holds 5 gallons.
I was going to pick up some non alcohol gas this evening and try that. In the process of checking the engine out I did find a torn up boot on one of the drive shaft u-joints and I'll have to take it to the dealer for that. I'll have them see if they can find anything.
One reason I liked this particular model was that it didn't have expensive computer systems to go Tango Uniform.

Bob

[oldred]

Good to know that screw was tight, every time I hear about surging or running uncontrollably wide open that's the first thing I suggest checking because of the damage it can do. Since this thread started and the subject came up I have spent a bit of time researching this problem and it seems Briggs has indeed addressed the problem and it should be a non-issue on engines built in the last three years or so.

[Boz330]

The screw in this one is upside down, so if it did vibrate loose it would end up in the manifold. I'm use to aircraft where every bolt is installed to minimize the bolt falling out.

Bob

[ohland]

http://pure-gas.org/

My Dad has a HISUN UTV, and it has been sitting in a machine shed for over a year with only occasional use (1hr30min one-way). It had issues with just running at the start, then he switched to 100% gasoline. Just went over today and changed the oil. Runs good.

[Boz330]

http://pure-gas.org/

My Dad has a HISUN UTV, and it has been sitting in a machine shed for over a year with only occasional use (1hr30min one-way). It had issues with just running at the start, then he switched to 100% gasoline. Just went over today and changed the oil. Runs good.

I put pure gas in it, hopefully that will work on this one.

Bob

[10x]

On small engines, check the air cleaner - a dirty air cleaner will cause an engine to run lean and surge.
Avoid fuels with ethanol as well - the local small engine mechanic claims to earn a substantial living off of ethanol enhanced fuels.