Ok, i guess a maxi tank holds like 3/4 or .8 gallons or some shit, so check this out: when my tank is like .4 gallons from full (full to the brim!!) it just wont run. The bike acts like it is out of gas and it seems like air is coming through the jet cuz i lean way out. Idle is high (like 4-4.5thousand rpms) and i can barely give it any throttle or it dies. Doesn't make any difference to run without the gas cap. It IS a ported and moded bike, but the problem did not arise when i did all this, it happend later. Now it gets worse and worse. (it started not running when it had only about 1/4 gallon, now it has to have at least like .4 gallons to run. Whats up? New petcock?