The carb fit right in,,, the stock boots worked fine,,although,,it IS a tighter fit than the stocker. Im NOT convinced that the boot running from the carb to the airbox is sufficient though,,I'm researching that now. It already has a "crimped" design from the factory, the 39 just makes it even worse,,,BUT,, it DOES run just fine like I said earlier. I'm using a 400EX thumb throttle to accomodate the new cable,,you CAN drill and tap the stock throttle housing. Just take the stock cable out of the assy and reinstall the throttle cap,,, you will drill the existing "slot" turning it into a tapped hole, said to work fine,,but I had a thumb throttle already,, so what the heck,,,the cap said "HONDA" on it,,,so I ordered a polished cap from NACS racing.