Cush Drive Question

[trevinoz]

That would have been some strip job, Trevor. In 1951 I was more interested in pedal and push power.
My point is that I have stripped many engines and have only found one scrolled sleeve.
Surely some of them if not all would still be wearing the original cush drive, it's not the type of thing which wears out regularly.
Further, I think that the case oil seal was introduced on the BA series engines.
These don't seem to have been very common in Australia but the ZA10 and iterations of the long stroke engine abound, I have a pile of damaged ZA10 cases but only one BA10 which I assume was an American import as it is stamped HC and had the triplex sprocket. Sadly it is beyond repair.
I could be completely wrong in my assumptions but the container full of cush drives speaks for itself.

[AdrianJ]

I have 53 plunger flash, with correct engine number, so i was surprised when I found the oil seal, which was not in the illustrated parts list.  I looked at a 54 parts list and there it is. I assume that though dated 53 my bike or at least bottom end were from the 54 model year. Did I read somewhere that the new model year started somewhere around August or September?
Adrian.

[trevinoz]

Is it BA10? I think that was the first series with the seal.

[Swarfcut]

Trev.... I reckon you are correct and the seal first appears in the BA7 and BA10 series of crankcases in 1953.  This BA Series remains unchanged until the end of Plunger Crankcase production. I have a BA10 driveside case dated 14/6/57, with a number just below 16000.

   The A10  of 1950, together with the A7 of that year are both ZA series, continuing on the A10 until 1952. The  A7 series changes to AA7  for 1951/52. There is no AA10 series.

  In summary it appears the cases originally had a slinger or a seal, depending on the year. The slinger type had a scroll to start with, as on the earlier Longstroke A7, but evidence would indicate this was phased out in favour of a smooth drive sleeve, which was later used with the seal.

 Adrian...   BSA changed model years in the Summer Holiday Shutdown during the month of August, allowing them to present their updated range at the annual Motor Show, ready for the following Spring. This is why model year follows the actual date of manufacture are slightly different, roughly a 4- 6 month leeway.

 Swarfy.

[AdrianJ]

Yes Swarfy and Trevinoz,
It's a BA10. I knew the production year changed early, but not as soon as the summer shutdown. At least that bit's sorted now. Just timed the engine, about to put the head on and try to start it. Very unsure about the back end though, but that should be another topic.
Adrian.

[BSA_54A10]

That would have been some strip job, Trevor. In 1951 I was more interested in pedal and push power.
My point is that I have stripped many engines and have only found one scrolled sleeve.
Surely some of them if not all would still be wearing the original cush drive, it's not the type of thing which wears out regularly.
Further, I think that the case oil seal was introduced on the BA series engines.
These don't seem to have been very common in Australia but the ZA10 and iterations of the long stroke engine abound, I have a pile of damaged ZA10 cases but only one BA10 which I assume was an American import as it is stamped HC and had the triplex sprocket. Sadly it is beyond repair.
I could be completely wrong in my assumptions but the container full of cush drives speaks for itself.

I will pay that one Trev.
I was a long way from seeing the light of day in 51 being I am 65 this year.
It is just one of my bugbears that people present with a latter or just plain wrong part and won't even consider that it just might not be the part that was there when it rolled through the despatch department doors.