Originally Posted By: wag123
As others have said, the jets are plugged with dirt, dissolved rubber, and/or varnish (from old gas) which must be mechanically/physically removed to allow the fuel to flow through them. Adding something to the fuel won't help because fuel must actually be flowing through those jets for an additive to do anything.
I have given instructions on how to fix this problem before, I will give them again.
1. Drain all of the fuel from the tank and fuel line.
2. Remove and disassemble the carb.
3. Poke a small STIFF steel wire through all of the jets, including the main jet found in some float bowl nuts (on the side of the nut on some engines, Tecumseh engines in particular). Do not use copper electrical wire, if it is small enough, it won't be stiff enough. I use the small steel wire found inside plastic twist ties, everyone has twist ties laying around the house. Don't worry about wallowing out the jets, you will only be poking through them.
4. Spray carb cleaner through all of the jets and passageways. Wear eye protection. Compressed air is not needed.
5. Clean-out any varnish and dirt/debris found in the float bowl.
6. Shake the float. If there is anything in it, replace it.
7. After re-installing the carb, check to make sure that the choke operates properly and the throttle linkages are installed and operating correctly. Adjust the governor.
8. Replace the fuel line if it is hard or cracked.
9. Refill with FRESH fuel, not just fresh from the gas can, fresh from the gas station! If your gas can has had gas left in it for a couple of years or if it has been left outside in the rain, get a new gas can.
10. After filling with fuel, let it sit for 30-45 minutes with the air cleaner off before starting. Watch for fuel overflowing from the carb. If so, the inlet needle (and seat in some engines) and/or float will need replacing. Some carbs will need to be replaced if this happens due to corrosion in the inlet seat, Honda carbs are famous for this.
I have performed this procedure many thousands of times and it works every time. The average mechanically inclined person can complete this procedure in less than an hour. Total expenditure, less than a dollar in most cases. The only times that the carb will need to be replaced are due to corrosion or excessive wear.
Awesome, thanks for the pointers. I'll check everything you mentioned and report back my findings.