Everything on this bike was a challenge. I bought the Grubee HD rear hub, and had to lace it up so that it was centered between the upper brakes. It barely made it. The drum brake housing went on easy with a small washer shim so that it wouldn't bind. Had to make a special tool to remove the brake drum. The drum brake makes a difference. With all the brakes applied, this bike will stop from 30 to 0 faster than you want it to. You won't see very many 4G's on a GT frame because the front motor mount has to be milled down so that the 2 front engine bolts recess into the front mount. I took a large drill on ground it flat, then recessed(milled) the motor mount so that the mounting plate would sit flat on the motor mount. The motor is in a fixed position, and cannot be slid forward or backward, but can be slid sideways. The tank vent needed to be trimmed to get air into the tank. It is a tiny rubber valve inside the cap that doesn't work.