I have an old Ariens ST824 Snow blower with a Tecumseh HM80 155316P (Ser. # 92790) engine. I rebuilt the carb last year. It starts good; however, it will not run smooth. There are always minor misfires that keep the engine from running smoothly. I can adjust the main adjustment screw (high speed) one or two rotations either direction and that makes very little difference in the way the engine runs. It continues to have minor misfires and the engines rpms vary somewhat.
Thanks for your suggestions.
HelloThere are many things that can help, none the least of are replacing the spark plug. How old is it?
I understand you just cleaned the carburetor, some of this may not apply, but still the information will be helpful.
I expect you have either a fuel Quality or fuel delivery problem Still..
As engines sit or get older, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems.
Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.
Today's gasolines contain MTBE and alcohol. (Ethanol) They turn to "Junk and garbage" very quickly. Alcohol absorbs water. And they call it "Oxygenated fuels! It is the oxygen (and the water) that breaks down the organic compounds in the fuel and turns the gas to "Garbage" (Gum and varnish) The fuels we had just a few years ago had no alcohol in it and would store for longer periods of time before going stale.
Fuel stabilizers do almost nothing to prevent the fuel from going bad with the changes in today's fuels. The whole point of a fuel stabilizer is to form an oily film on the surface of stored gasoline whether in the tank or in a gas can. The idea was to keep oxygen away from the gasoline to prevent breakdown. Since the fuel is already oxygenated, the fuel stabilizer concept is null and void. These fuels start to degrade immediately upon the addition of the ethanol.
Do not buy gas from the "Discount" Stations. The discount stations get a reduced price on gas because they may be buying fuel that is nearly 30 days old already. You may be getting fuel that's nearly stale right from the pump when buying from a discount station. Purchase your fuel from the well-known stations such as Shell, BP, Sonoco, Phillips 66 etc.
More than 70% of all of our repairs in our small engine repair business are due to these same issues. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carburetor.
The carburetor will need to be cleaned and overhauled as well as the rest of the fuel system.
In an Emergency such as a blizzard where you cannot get out to buy a carburetor kit until the plows come through, or during an emergency power outage and you need a generator running even if it runs poorly, you might try the following if your carburetor is the type that has a bowl. Sometimes this procedure works:
While the carburetor is still mounted to the engine:
You may be able to finish the job at hand then clean and overhaul the carburetor correctly when you have more time and a new carburetor overhaul kit.
If you don't feel comfortable with these kinds of repairs, or if the carburetor still doesn't work correctly after your attempt, I would suggest sending it to a profession repair shop with a reputation for having friendly, knowledgeable, experienced service technicians. It would be best to take it to someone who has an "Ultra-sonic" cleaning machine. This machine uses a very mild carburetor cleaner in concert with ultrasonic vibrations to get the very small passageways clean. This method is very effective even when traditional methods fail.
Please feel free to ask follow-up questions so that we can always arrive at the correct solution.
can you manually manipulate the governor assembly while adjusting the carb.
You should be able to rev it up quickly and smoothly when the carb is adjusted properly and good and clean.
There are two sides to the carb, the low speed and the high speed.
I will be that there is one little oriface somewhere that is still plugged up.
Perhaps underneath a welch plug (that is why I say use a carb kit..
If it runs all the time whithout stopping then the ign is good.
Compression is OK or else it would not start easy.
Is it possible there is a bloackage in the muffler?
Perhaps a dirty fuel filter or dirty screen in the gas tank?