So what year and/or engine number did BSA change from 5/16 to 3/8 inch cylinder base studs on the A65? Any other changes during this period make the later-earlier engines incompatable? I know that the earlier and later head/valve cover are different. Anybody?
Gee, not only the size, but the location of the two center front studs changed as well. Still, you can put a later barrell on an early set of cases, you just have to do some drilling and put on some nice hardened washers.
The clutch actuation and shifter mechanism changed as well.
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Re: A65 Cylinder Base Studs#32735 01/08/087:17 pm01/08/087:17 pm
the oil pump also changed from die-cast alloy to cast iron (I think 69 but not 100% sure), if using the latter cast iron ones with earlier cases you will need more clearance inside the timming side inner cover, the latter ones had clearance cast in
probably the most majour difrence between the pre66 and latter cases are the arangment for the main crank bush. The machining of the cases is totaly diffrent to accomidate a narrower bush (across the flats), diffrent side thrust arrangment etc
"There's the way it ought to be and there's the way it is" (Sgt Barnes)