Oil level in d/shaft twin shock

[cringe]

I know it seems a stupid question,but how do you check you have the correct amount of oil in the d/shaft on a 1981 R65? In the book it states draining and refilling with 150cc ,then inserting a rod through filler on to shaft ,it should show oil on rod 2mm,but does not show with extra 20 mm put in !

 

[wreck diver]

I pressume the bike is on level ground and the rod is on the shaft and not gone past it.

 

[cringe]

oil level in drive shaft

Yes bike level and rod on top of shaft,does it do any harm too much oil in d/shaft?