my friend has put 10 tanks through his car, and still the max speed is like 20 what should we do to fix the problem? or what could it be? we have leaned it out about 1/2 a turn, what else could this be?>
Sounds like its really rich top end. You will need to screw in the top end needle. If its that bad try 1 full turn.
Make sure you run it on the track along a straight at full revs for at least 3-4 seconds as the engine needs to clear the mixture in the crank before it sees the effect of the adjustment. If it worked the engine will pick up and rev well aafter 2 seconds.
Another problem could be that the head clearance is too big. Take out the plug and insert a piece of solder into the head and turn over the engine by hand. The piston will flatten the solder against the head.
remove the solder and measure with a vernier. It should be about 0.018" or 0.4mm
Make sure you are running a hot plug. C5 TGF Novarossi