A50 Rocker Arms

[rutofglos]

I am returning to the road an A50 first registered in 1963. About to replace the rocker arms in the cylinder head. Checked the part numbers on the rockers I removed some months ago to find they are different from the ones in the appropriate parts book viz: Exhaust LH 68-0152 RH 68-0154 Inlet LH 68-0150 and RH 68-0148. Checking all available BSA references on line it seems all A50/A65 had the same rockers, not these part numbers. A Google search brings up no general info only a US parts supplier offering for sale as NOS the Exhaust LH rocker. as part number 68-0152 described as for A65.

Can anyone advise? Can I use the rockers I took out of the engine despite the different part numbers? Do I need to measure the arms to ensure that they are not too long?

The bike was a dead dog but turned over (not seized) with low compression. Bottom end has been refurbished by SRM and bores re-lined to standard with standard NOS pistons fitted.

[JulianS]

The numbers on the rockers are the forging numbers and the numbers in the parts books are the finished component part numbers. Quite common with BSA parts.

[rutofglos]

Thank you very much indeed for the prompt and most helpful explanation. What a daft system...

[ChrisG]

Not really that daft.
In manufacturing, its quite normal to have different part nos for raw materials, semi finished components and the final article. It often happens when the same raw material, forging or casting for instance is used to make a number of different finished parts.
Hope that clarifies.