Motorcycle Repair: CARBURATOR, vernier caliper, air fuel mixture

Question
QUESTION: I HAVE AN 83 ATC 110 IT SEEMS TO RUN ALRIGHT BUT WHEN IT GETS WARMED UP WHEN YOU GO TO GIVE IT GAS IT SPITS AND SPUTTERS AT THE LOW END THEN PICKS UP I CHECKED THE PLUG ITS PRETTY BLACK SO IM GUESSING IT NEEDS TO BE LEANED OUT WHAT SCREW IS THE AIR FUEL MIXTURE AND DO YOU KNOW WHAT THE SETTING IS SO I CAN LEAN IT OUT A BIT

ANSWER: Clint, this sounds like more than just an idle adjustment problem.  It sounds like the air filter could be seriously plugged or the float level is too high in the carb.  The idle air screw adjusts the amount of air in the low speed circuit.  If you turn it in, it reduces the amount of air and increases the percentage of fuel.  If you want to lean it out you can back the screw out a turn or two.  I don't think that will fix the problem, but it's easy to try and find out.

Regards
Rich

---------- FOLLOW-UP ----------

QUESTION: THANKS FOR YOU HELP RICH I CLEANED THE AIR CLEANER REALLY WELL AND IT STILL DOES IT HOW DO YOU ADJUST THE FLOAT LEVEL? AND WHAT WAY DO YOU THINK IT NEEDS TO BE ADJUSTED UP OR DOWN? WITH THE PROBLEM IM HAVING? THANKS...CLINT

Answer
Make sure you squeeze out as much oil as you can if you are using a foam filter.  If there's too much oil it will cause the problem you describe.  

You'll have to lower the float level.  Inside the carb you will see a float with a small metal tab the contacts the needle.  You have to bend the tap up a small amount.  I wouldn't recommend trying to adjust it by eye or trial and error.  You can put a hole in piston if you run it too lean.  You need a vernier caliper or a float gage to properly adjust the floats.

I'm afraid I don't know what the right level should be but it's in a manual if you happen to have one.  If you don't have a manual, lower the floats one mm at a time until the engine runs right.

Regards
Rich