Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Old cases and pistons

https://imgur.com/kEeuucz



I'm putting an engine together for a spare for the racing rig.
wondered if anyone had any idea what these are, they are very nice, like brand new
but the numbers look a bit suspect to me. Not really important as they have been machined
for the end feed and needle race etc but just wondered if the number is Kosher.
Got a set of pistons as well, 68-743 think they are 10-1's but not sure.

Does look odd, I have only ever seen the dots between numbers on pre unit cases before.

Probably just a set of replacement cases i think.

Putting the 3/8 barrel base studs in 'em will ruin any originality anyway, as will
doing the end feed.

That fits, early cases replaced early in A65 life by a mechanic used to Pre Units hence the use of dots.

Looked in my list of engine numbers

I have

A65.A.18x (20C below the A65) I identified these as 1964 A65 Star

A65.C.227x 1965 Rocket (with rev counter)

I guess yours are very early , 1962?

Ray

The stamping is original to your 1962 cases. I have a nice unmolested 1962 A65,nine digits earlier, and the stampings are identical.

Dots in the stampings were used up into the mid '60's.

The 1966 parts books shows std Piston 68-742 as 10.5 to 1. The piston would be marked 68-743 with BSA going 1 digit higher on the actual part. The 66 book is the only place I could find those pistons, not in 65 or 68.

Gordo

As Gary and Tim said, these look to be very original cases and stampings. I think the stamps changed around 65 about the same time they stopped using the dot.

HC, as we know from the pre units being high compression, I’m not sure if the Rocket models (which had high compression pistons) were marked A65 R **** or just normal group of stamping and HC added as your photo???

Thanks gentlemen, blimey '62 that means they are truly eligible for period 3 racing here.
That make's a change...... lol.
You can really see the difference between these and late '70+ cases though, these are
crap when compared to late ones, nowhere near as strong around the gearbox area.
The gallery plugs were impossible to remove and had to be drilled out, even things like
the depth of the oil pump fixings much shallower. It certainly highlights the changes made
to improve them over the years.

The pistons did not come out of that motor BTW.
They are spitfire pistons ? That's good, they are in very good condition as well so i'll stick a set
of rings on those and give the barrel a hone once i've drilled it out and slotted the 2 front fixings.

look just like the markings on my '62. don't remember where I read it but HC means high compression.

My 65 rocket is stamped A65 C xxxx

The very early A50s and A65s had a compression ratio listed in the parts catalogue as 7.25:1. These pistons are flat topped, I had a pair in a 66 Lightning with a Spitfire Mk 4 head and 32mm carbs. Probably the most tractable BSA twin I've ever ridden with masses of pulling power. However back to the point; there were some 8:1 pistons available, can't remember the part No, I have a pair of A50 ones somewhere. I think that early engines fitted with these were stamped HC. My May 1965 Cyclone motor is also stamped with dots.