Thick flange cylinder

[Rich mackie]

Can anybody help with this number, local advert selling a A10 thick flange barrel with a part number 56-7209 ?  Numbers I can find for my 58 is 67-1210 any info would be greatly appreciate

[Swarfcut]

  No Mystery. The number 56 7209 has been misread or your typo. Its actually 56 7029. It is not a part number, it's a BSA PATENT Number and appears on all barrels. So same number on A7, A10, (Standard and Thick Flange) variants, plus early narrow and later wide fin types. It's the number on the back of the tappet housing. First seen on the A7 Longstroke.

 Barrel part number is cast on the front face of the mounting flange. 67-1210 is correct for a thick flange wide fin barrel. Look for a bore of less than plus 60, giving scope at least for one other simple rebore, then consider broken fins, cracks, pulled threads. These frequent faults detract big time from it's value but are fixable, while adding substantially to the cost if requiring professional repair.

 Swarfy.

[Rich mackie]

Thanks for the info, so the 1210 is the one too look for. Is the wide and narrow fin the same part number ?

[Swarfcut]

 RichM   Early narrow fin A10 barrel is 67 253. This uses a matching narrow fin cylinder head so no good for you. It fits, but looks strange. The thin flange wide fin barrel is 67 1074, used on later Plunger bikes and early S/A and is interchangeable with the holy grail thick flange barrel, 67 1210. Cylinder base studs need  to suit the flange thickness of the barrel eventually used. Thick flange ones are just that bit longer.

 Swarfy

[Rich mackie]

Thanks swarfy, I'm totally new on the bsa, as you've probably worked out 👍 appreciate your help

[BSA_54A10]

Visually the early barrels are really round looking like a fat single
The late thick flange is quite square

[Greybeard]

Visually the early barrels are really round looking like a fat single
The late thick flange is quite square

Like mine?

[groily]

I think more like the one here GB - but as IKBA about model variants  . . .

[JulianS]

The large fin barrels were introduced in late 1953 and the large fin with thick flange was introduced around May 1957 for the Rockets and DA10 series Golden Flash models.

Greybeards photo shows a big fin thin flange barrel.

[sean]

I vaguely remember reading a few yrs back
  that someone was looking into reproducing the a10 cylinders in alloy ...I would happy with cast iron ones as I just replaced mine with liners total cost was probably more than half the cost of  new cylinders and a 5 month wait in a machine shop .
good thick flange cylinders are getting hard to find .

[muskrat]

G'day sean.
This may be the ones your thinking of.
https://www.a7a10.net/forum/index.php?topic=13729.msg113576#msg113576
https://www.a7a10.net/forum/index.php?topic=13729.msg117894#msg117894
https://www.a7a10.net/forum/index.php?topic=15404.msg130101#msg130101
Cheers

[sean]

That’s it thank you for finding it …I thought my memory was going….wonder if any of the prototypes made production

[Beeza]

Second that from me,  re production?
 We are definitely going to run again at Lake Gairdner next year with Road Rocket 201. And we are/have  already made many changes and modifications to the bike so far, and there is definitely room to use an alloy barrel of this type at this stage, so we would be massively keen on availability of such beast of a barrel.
With the slightest glimmer of hope.
Thomas, BEEZA , cheers.