I just added a HMF Utility Slip-on Pipe to my 650i and rejetted today. It wasn't too bad. I think it took me about 2 1/2 hours. You've got to take the side plastics off and the airbox. Then you have to take the bowl heaters, fuel line, throttle cable, loosen the clamps on the carb boots and pull it part of the way out. Then you have to pull out your starter plungers and remove your vent and drain lines. Putting it back in after changing the jets seemed a lot easier.