Well stop putting lead substitute in it to start with, youll just glog the carb up faster. It doesnt say "leaded fuel only" it says "do not use unleaded gasoline", as I have come to know the story, this is because during the 70's gas crisis people were trying to use white gas, i.e. coleman camp stove fuel. Unleaded gas runs em' just fine, and I use a little over 3 ounces of penzoil 2 cycle oil per gallon of gas in my 80' puch newport, which is nearly the same bike as your maxi.
Hope that helps,