Crankshaft Design for the Twins.

[bruv]

Dear All,
I have two crankshafts, side by side on my workbench. Both items are for a 1958 600c, but I would imagine there is no difference when looking at those for the 650cc variants. I've noticed that one of the crankshafts has 3 oil delivery hoes in each Big End journal. Each delivery hole is spaced at 120 degrees around the circumference of the journal. The other crankshaft has only 2 oil delivery holes on its Big End journals. These holes are spaced at 120 degrees between them, but give the impression that someone has forgotten to drill the 3rd hole in the journal !! My question is :- Is this normal, or am I looking at a machining error during manufacture ?? My workshop diagram for the 1958 crankshaft shows 3 holes as described above. Any help would be most welcome please. I don't want to fit a crankshaft into the bike that has 33% of its big end oil supply missing. Safe riding to all, kind regards, Bruv.

[1608]

The 650 cranks are different, they have a longer stroke. This gave the desired gain in cc without having to enlarge the bore. Can't help about the oil holes, but don't suppose it makes any difference.

[matchless]

I have found (It may be a coincidence) that AJS cranks were drilled with 3 holes and Matchless with 2 holes. Both work OK.
Regards..............David