Pull the tank off and take the petcok off, get yourself 2 gallons of White Vinegar and a couple of handfuls of coins. Put the coins in the tank, plug up the petcok hole, pour half a gallon of the vinegar into the tank. Shake it up like crazy for a few minutes. Then drain it and take all the coins out. Then fill it up completely with the vinegar and let it sit overnight. Clean your carb. and petcok. The following day, drain the tank. Pour a few cupfulls of fresh gas (not premix), shake it up to flush out the vinegar and then drain it out. Put the tank back on and your done.