Most likely you have a fuel delivery or fuel quality problem.
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 or needing to finish the final two holes of the best game of your life, 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.
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Have you checked the compression to see if it is low?
For whatever reason, the unit is running too lean..
It is either not getting enough gas or on the flip side, could be getting too much air.
Make sure there are no air leaks anywhere.
Could be a bad gasket, a warped facing somewhere that a gasket normally is enough to help two surfaces meet.
In old lawn-boy lawnmower engines, it could mean clogged exhaust ports or bad reed valves that are to close on the power stroke.
Could there be a clog in the muffler or exhaust ports?
I do not mean to be disrespectful of your abilities, but I think you may have to look at the possibility that you missed something in cleaning the carburetor. Some tiny port or hole that needs to be soaked, drilled out with a tiny stiff wire, or blown out with air.
Also, the gas does not have to be "in the tank" for longer than 30 days. It could have been stored in a Gas can that long and still have gone bad.
Head Gasket, Intake gasket, cylinder gasket, fuel filter?
Just keep thinking....
Too much air, not enough gas, lack of compression, wrong mixture, fuel quality...
Check to make sure the spark plug is the right one and is perfect. Must ignite at correct temp.
The answer is there.
That is exactly what I am telling you.
Have you ever noticed that the gas prices seem to dip about the same day every week.
Around where I live it is Wednesday (sometimes Thursdays).
The want to make sure they run as close to totally out as they can so they can fill their tanks up with NEW gas.
Then when the tanks are full, the prices go back up.
If at the end of the cycle they do not have much gas left over, they do not lower the prices to get rid of it.
Many of the cheap stations buy gas from the refineries which are nearing the 30 day old mark. When you buy it from these discount stations, the gas is almost already breaking down.
Now days, we call this "just in time processing" and just in time inventory control.
The refineries can store OIL for long periods of time.
The refineries can store the components of gas separately for long periods of time.
The refineries can store the gas for long periods of time before it is blended with alcohol.
As soon as it is blended with the alcohol, the time clock starts because the oxygen in the alcohol starts eating away at the gas, crystallizing it, and turning to varnish and gum.
You do not have trouble in your car, because almost never do you have the same gas in your car longer than 30 days.
Also, there is a huge difference between winter blend and summer blend gas.
They should never be used "off Season".
here is just one excerpt from an article on the subject.
Today as I write, I am sitting just two blocks from the Atlantic Ocean in our Fort Lauderdale, Florida office, atop a 10-story high rise on the Gulf-Intracoastal Waterway. This has me thinking. The tenants of our beach-front high rises, vulnerable to devastating storm surge, have no idea that the emergency services they'll depend upon may not be available--all because of a simple oversight. That neglected item is fuel. The service technicians that work on back-up generator systems tell us that about 70 percent of engine failures are fuel-related. I'm not surprised. Given a little heat, moisture and time, the oxidative process takes over quickly on today's stored fuels, creating gum, resin and varnish--cholesterol for a major engine coronary and power shut down.
A surprising number of engineers responsible for maintaining back-up power supplies for telephone companies, public utilities, hospitals, high rise apartments and condominiums are unaware that fresh fuel can go bad in just a matter of weeks. But you don't have to be left in the dark.
Have your own power generation source for one. Then make absolutely sure your fuel supply is in good condition. To ensure that fuel quality will be good for years requires only a few basic steps.
The problem begins with today's modern fuels. These so-called "clean" fuels typically deteriorate at much faster rates than fuels made 20 years ago. While all fuels suffer from the problem, most at risk are the EPA mandated reformulated gasolines (RFG) that contain oxygenate additives, derivatives of methyl alcohol and ethyl alcohol. We've seen gasoline have shelf life as little as a month--particularly if it is subjected to heat and moisture.
Diesel fuels fare a little better, but not much. Most all diesel fuel, including the EPA's mandated low sulfur version, has shelf life of from 3-to-6 months. Again, this varies widely. Recently we tracked a diesel fuel produced at a refinery in Texas to its final destination in Florida. When tested at the refinery the same day it was produced, the fuel barely met the specification for stability. After being stored, pumped into a coastal tanker, offloaded at Port Everglades, stored again, delivered to the fuel jobber, and finally to the customer, 23 days had passed. Again the fuel was tested. This "fresh" fuel now tested out of "spec."
In part, this has to do with new processing techniques developed by refiners in recent years. While the new refining methods are more efficient, producing more gasoline per barrel of crude, these fuels are often far less stable than the conventional "straight run" fuels we had before.
To make matters worse, the quality of the crude oil feedstock going into the refinery changes daily with each shipment. Processing equipment must be precisely adjusted to these varying qualities, but it doesn't always happen. This neglect results in poorly processed, less stable fuels. One oil company survey indicates that at least 50 percent of the gasoline sold today is substandard.
Oxygenated fuels are also less fuel efficient, giving a minimum drop in fuel economy of 3 percent (if you believe the major oil companie--much higher if you listen to those among us who are fuel misers and check mpg regularly.) Additionally, there is strong evidence that these fuels pose dire health and environmental consequences. Public interest groups have assembled a large amount of data on the damaging effects of oxygenated fuels.
A good source on the World Wide Web for this information is the Oxybusters of Texas Web site at http://www.oxybusters.com/casehist.htm. A good basic overview of oxygenated fuels is located on Chevron's Web Site at http://www.chevron.com/prodserv/bulletin/oxy-fuel/. I strongly suggest you check these sites out and educate yourself on issues you'll rarely see in mainstream media.
First, you said you checked the fuel pump.
Then I said Clean the carburetor and gave very detailed instructions.
Then you said you already had.
I also said it could be fuel quality.
I also said:
check the compression. You said you can, but did not provide results.
unit is running too lean..
it could mean clogged exhaust ports or bad reed valves that are to close on the power stroke.
Then I said I think you may have to look at the possibility that you missed something in cleaning the carburetor.
Some tiny port or hole that needs to be soaked, drilled out with a tiny stiff wire, or blown out with air.
The I detailed fuel quality problems.
"Also, the gas does not have to be "in the tank" for longer than 30 days. It could have been stored in a Gas can that long and still have gone bad.
I summed up saying.
Then you argued with me on fuel quality and how long gas stays good.
So I provided a third party Write up with links to support my position on fuel instability over 30 days.
The you Stated "told me to do what I already did!!"
Said you missed something when you cleaned the carb.
And, that I said take it to a pro if you can not figure it out.
Well, If you are going to argue with the advice rather than take the advice, then no one is going to be able to help you.
I stand by my answers, and am insulted that you think that all I said was do what you already had done again.
I will revise my statement. If you can not follow the steps that I have given you and take the advice that is being given to you in good faith, then you need to take it to a pro.
I will opt out so that someone else can help you if they think I have missed something.