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Based on a sample of 74 gear sets, this graph shows the frequency of the different gear sets and the spread around the target dimension of +0.

  Click thumbnail to open the list. R24 – R27           R51/3 – R68           R50 – R69S            

Flow chart to identify a 2 cylinder crankshaft. Click on the flow chart and table for larger images, click <- arrow in your browser to return to this page.                                                            

This list shows the part numbers for all parts that need to be changed in case of a conversion to 12V  

3 different breather plates have been used on the boxer engines:

Table with part numbers Click here to view a larger table  

This modification and upgrade, using BMW components, results in a lower-ratio gearing for R26, R27, R50 and R60 gearboxes producing smoother, robust and responsive performance especially in 1st, 2nd and 3rd gear changes while 4th gear is unchanged. The “S” gear ratios allow the rider to accelerate smoothly through gear changes by letting the motor rev freely through an optimum power-torque range. Although the 3rd gear of both gearboxes have the same number of teeth, they are different: The standard gear has a diameter of 65.6 mm and the S-type gear has a diameter of 65.2 mm. They have a
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Overview of the different crankshaft shims used in the boxer engines

Piston and cylinder clearances for BMW R50, R60 and R69S (also valid for R50S and R69)

Wheel offset for R51/2 – R68, R50 – R69S models (from “1000 Tricks für Schnelle BMW’s”)                

Overview of  BMW motorcycle models produced from 1948 to 1969 (specials not included) Click for larger image: Models & Production Numbers  

Overview of the different valve types and related components, used in the BMW 1 and 2-cylinder motorcycles 1948 – 1969