Sunbeam 3-speed gearbox bearings, 1928 and 1929 onwards

Thanks to Chris Fisher for suggesting suitable quality bearings for the 1929 onwards 3-speed gearbox I’m putting together at the moment. The gearbox will be a CT close ratio type and is for a 1928 Model 6 that has been modified in the deep and distant past to house a hybrid OHV motor. The motor employs 1930/1931 crankcases with 1927 single port head breathed on by Chris Odling to take a new Amal 289. So, the whole bike is a “bitsa” but now goes very well with a 7.5:1 forged Model 90 piston from the sunbeamland shop.

I might point the “Model 69″ up a couple of hill climbs once the gearbox rebuild stops it dropping out of 2nd gear and we fit a 19” rear rim – it will then take a pair of the excellent Avon race compound Speedmaster and GP tyres.

1929/1930 Bearings:

  1. 1 off RHP LJ1-2RSJ
  2. 1 off RHP MJ7/8-2RSJ
  3. 2 off RHP KLNJ3/4J

The earlier 1928 wide case box has a smaller mainshaft diameter and consequently an RMS 6 bearing in the case rather than the RMS 7 of the later type. In this case the RHP MJ3/4-2RSJ looks like it could be a good fit.

1928 Bearings:

  1. 1 off RHP LJ1-2RSJ
  2. 1 off RHP MJ3/4-2RSJ
  3. 2 off RHP KLNJ3/4J

With the outer bearings being sealed it might be a good idea to consider implementing a small breather hole in the gearbox filler cap.

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