Forum bmwbike.com

The R51/2 has marks on the chain sprockets of camshafts and crankshafts.
Is the timing correct when marks of camshaft are facing each other and mark on crankshaft is pointing vertical upward?

YES Ivo, that is exactly how to set up the timing.
I have a workshop manual written in French that has a clear illustration of a R51 timing chest.
The last R51 engine I rebuilt was a racing engine timed with a gear train, but unmarked! That took a bit of working out.

Good luck, Gerry