This new single downtube rigid frame is designed to utilize a four-speed transmission instead of the old three-speed unit We designed a special engine sprocket for Big Twin dual row primary chains and positioned the transmission mounts so that the conventional primary drive components and special Paughco covers from an early 74" Big Twin can be fitted to the bike Because the engines, transmissions and drivetrain components are both plentiful and affordable, you can build a great little 45" powered solo and customize it any way you want, for a fraction of what a modern bobber might cost you For those who don't want to deal with a wet clutch, BDL has designed a belt drive unit, just for this application The transmission mounting plate 630-967, exhaust, engine sprocket, BDL Open Belt Drive Kit, oil tank and axle kit must be purchased separately 35° rake, backbone 0" out, downtube 0" up