Originally Posted by larryboy
I'm actually trying a small Magura clutch master to save weight, we'll see if it can move enough fluid.
The OE master bore diameter is 16mm and the slave is 24mm. Based on the 'engagement range' of the OE clutch I'd guess that a 10% smaller master bore diameter still might work. Say 14.5mm as a minimum diameter.
But since Magura makes the OE BMW master, you might find a 16mm Magura part. If so, on the old and new clutch levers check the centerline distance between the clutch lever pin and the piston pin. For the same bore diameter, that dimension determines lever throw.