I have a 18 hp briggs twin mounted in my old John Deere 111 rider chasis. I have a 6" pulley on the engine (stock was 3") and a 5" pulley on the tranny (stock was 7"). There is no more room to change the engine pulley, plenty of room to change the tranny pulley. It goes pretty good, but I want to be able to pull wheelies. Don't ask why, just like to entertain the neighbors . Is there anything else I can do? Motor is all stock, tires are all stock, stock 5 speed peerless transmissioin.