[kopcicle]

This may seem odd on the surface but several of the crankcase bolts are subjected to significant oil pressure within their length . If my gray matter hasn't deteriorated completely you are probably looking at case bolt around the counter shaft . One or all three of these 6 x 95mm bolts had copper washers under the bolt head flange (integral washer type) . Try carefully removing the offending bolt , cleaning the threads in the case with solvent and air pressure , installing an annealed copper washer and retorquing to spec . Better if you can post a pic of the offending bolt .
Then again I might have had too many drugs in the 70's . In that case disregard and have a nice day .