What's best way to clean a bad gum up caborator with old fuel on lawn mower?

The float may be stuck. Has it been sitting for awhile?. Gas gets old and gums everything up. Any engine that gets used sesonaly like lawn mowers , boats, generators, ect should have the carb cleaned every year so it can mix fuel correctly. Fuel stabilizer can reduce the frequency this needs to be done if used right.

Yes this is the semi automated startup process. If the fuel is bad(old) or the carburetor has residue restricting the fuel passages the engine will run lean requiring some enrichment.(choke) I suspect that the engine may be hunting when warm. Use carburetor cleaner along with a fuel stabilizer.

Check/replace the fuel filter.

Empty fuel tank and purchase some no ethanol from home supply running the engine will assist in cleaning the passages. When engine is running close the choke a fuel times to give the engine a poor mans clean out, Avoid disassemble of the carb with out having technical compliance.(these are delicate and susceptible to contamination).

Never leave fuel in the engine when in storage. Ethanol gums up the fuel passages.

Hope this helps?

Service the carburetor... this is a carburetor fuel air ratio issue...

If you have never done this procedure, go on you tube.com

Type in " how to service a 4 cycle carburetor"

Many videos will show up... best way to learn.. get some carburetor cleaner like gum out from advanced auto or dollar general etc... get some thin super thin wire to clean out the passages in the carb.. Spray into every hole you see..and if you have an air compressor, blow the holes with high pressured air...

It will then be able to run without stalling now that there is no gummed up passenges

Lawn mowers are a load of fun, aren't they? After a clogged air filter, the most common cause is fuel starvation, generally with one of three culprits: (1) A gummed-up carburator; (2) gunk in the fuel line, or (3) old/watery fuel. When was the last time you tuned-up the carb?

it does sound like a carb issue it may need to be rebuilt also check your fuel line and if you have a fuel filter check the filter clean the gov. assembly with carb cleaner

You have a dirty carb, start off by cleaning and draining your carb and your fuel tank, remove the fuel bowl on your carb and use a spray can of carb cleaner to clean the tank and carb bowl. be careful not to ruin or loose the orings that seal the carb bowl,,put it back together with fresh gas and you should be ready to go for the summer. always be sure to add fuel stabilizer to you fuel to keep your gas from going bad and gumming up your carb,.. You can get the stabilzer at any parts store even wal mart has it it the automotive section of the store..

Sounds like the carburetor is gummed up. Short of taking the carb off and cleaning, some good fuel line/carburetor cleaner such as Gumout (available at any place that sells auto oil/filters, etc. Wal-mart, K-Mart, Autozone). Put a bit of fresh fuel in the gas tank and add about 2 or 3 Tablespoons of fuel line cleaner. Start mower and let it run a bit. May run rough, but should clean the carb out unless plugged bad. If this doesn't work, the carb will need to come off and be cleaned. Can be done by the homeowner, but if you are nervous about tackling this job it may be best left to the mower shop.

Carb is most likely gummed up and will need cleaning. Anytime a gas motor is store through a season, you should use a product called "stabil" in the gas to prevent gumming up. Also check that there is a strong spark coming from coil. To do this, remove spark plug, hook it up to the coil and set it on motor block and pull it over. You should see a strong spark. If you don't see the spark, then either the coil is faulty or the magnet from coil to flywheel is not getting good contact.

carb is gummed up from the old fuel turning to varnish and clogging the jets. while trying to start, its trying to inject fuel, but its clogged and taking the path of least resistance (coming out the air filter).

you'll need to drain the gas tank and remove the carb to clean it out. if unfamiliar or uncomfortable doing this, then take it to someone to do a carb cleaning.

No it's sounds like the float in carb is stuck I've had 3 motors do this I put a fuel shut off in the line after I cleaned the carb out and rebuilt it. The problem is the gas breaking down an gumming up the float in carb. Drain the oil and an run some oil thur it to get the old gas out make sure you clean the carb out to.