converting a standard long stroke engine to Star Twin spec

[pdg]

I'd like to build up a 1949 Star Twin engine. Does anyone know what would need to be changed in a standard '49 long stroke engine to make it a Star Twin? I'm guessing that most items are common, but I'd need to find pistons (to make the higher compression ratio), head? (for the same reason as the pistons, though hopefully not), camshaft ?, pushrods?, ...? The Star Twin also came with twin carbs, but I'm not sure if any of the other external parts like the mag etc would be different?

Grateful for any help.

Regards, Peter.

[trevinoz]

Compression is marginally higher and twin carbys but the rest is standard A7.
The valves have a different part number but seem to be the same size.
The inlet ports on a standard head can be modified to accept the inlet adapter.

[pdg]

Many thanks. When you say "The inlet ports on a standard head can be modified to accept the inlet adapter", what do you mean by the "inlet adaptor"?

Regards, Peter.

[bikerjohndavies]

If you look at this listing there is a picture I posted of the twin carb manifold for a Star Twin and further down is a picture showing the recesses in the inlet ports for the protrusions on the manifold. Do you have a set of Star Twin crankcases? They would be the same as standard A7 except the number would be ZA7S nnnn where nnnn is < than 4000.

www.a7a10.net/forum/index.php?topic=10864.msg81517#msg81517

[pdg]

Many thanks for the information about the head. Is there any difference in the crankcases between a standard long stroke and the Star Twin, and did they make the higher compression ratio by removing a shim between the crankcase and the cylinder barrel or by different pistons?

[trevinoz]

Same cases, different pistons.