CP Burman Gearbox reassembly

[Paul D Carroll]

I have recently replaced the 20 tooth 4th gear in my 1951 G80S gearbox and while the inner cover is not in place I can select each gear and neutral easily enough, although I cannot select any gears when I reinstate the inner cover. When the inner cover is back in place the mainshaft is pushed back out by 5mm or so and the gearbox locks up and I cannot select any gears.

It appears as though the selector camshaft also needs to be moved out a little to select neutral, when the inner cover is not in place. I broke a tooth off the 4th gear some time ago and it has not caused any problems to date but it was about time to investigate and fix the problem.

I thought the reassembly would be a simple task, but it appears not so. Any help or suggestions would be appreciated

Regards

Paul Carroll

[clive]

If the only thing you have changed is the fourth gear, have you checked that the dimensions of the two are exactly the same?

[Andy51]

Hi Paul, I don't know much about CP 'boxes but I am fairly well genned up on B52s, and Clive may have a point. I have put together several of them and the final drive gear wheels do seem to differ in length/thickness (I have never tried them in different 'boxes to see if they are interchangeable but the teeth are definitely longer axially on some sets) although the part numbers remained the same across the years. It is quite possible that the same would apply to earlier 'boxes. Wherver possible, gears should be replaced in pairs. Hope this helps, Andy

[Paul D Carroll]

Thanks Clive/Andy51

I have checked the two gears and they are identical in dimensions, so I doubt if that is the problem

Paul C

[RayBeech]

Hi Paul, may be a red herring but I had a similar problem on my CP. After three assembly attempts I found the thin spring in the kickstart pawl gears was riding up so that as I tightened the nut on the end of the shaft it was trapped behind the end of the shaft/mechanism and so locking the gearbox up - but it was not 5mm so may be a different problem.
Ray.