Just a quick note for anyone considering or about to fit a Nova six speed gearbox to their CB450.
As in all cases hindsight is gold. When you look at the Nova website they will tell you that the only modification required to fit this gearbox whilst still using the Honda wet clutch is to machine the centre basket boss a bit so you can get a socket on the nut on the input shaft. (replaces the factory circlip)
Be aware this is not the case.
To fit this gearbox, in order, you need to do the following:
1) During the dummy fit up you will find that the 6th gear selector fork will hit a boss (selector drum bearing retainer screw boss) on the inside of the cases and prevent correct selection. You need to remove material in that area to ensure the selector fork has free movement.
2) Machine the inner clutch hub lip away so you can install the shaft nut using a socket.
3) Remove approx 2 to 3mm off the end of a brand new input shaft and then machine the inside centre of the clutch pressure plate. Because the new input shaft is approx 10mm longer than the factory shaft, you cannot get contact between the pressure plate and the clutch plates. You need to have both full contact with the plates and clearance at the lifter to ensure the plates are fully engaged.
None of the above is earth shatteringly difficult or expensive if you can do it yourself, it would just be nice to know before you start assembling everything.
It would take Nova about 35 seconds to put together some installation instructions.