I have acquired a bare BSA head recently, and I would like to identify it, if anyone out there can help. It's a single cylinder 650 head with casting numbers AM 68-72. I'm pretty sure it's an A65T head, but what year? The threads are all 1/4-26, if that helps. I might want to rebuild it, and it seems that the valves and guides are different for different years, and this one did not come with valves or guides.
P.S. Also, the intakes are not quite round at the entrance, as though someone had enlarged them, but it looks like it was done with a machine. Normal for this head?
Hi John. I think you mean itís a single carb, twin cylinder head. The A65T head probably looks similar to an A50 one so if your not sure check the cylinder bore dia. It should have a manifold on the back with a 28mm Dia inlet. The A50 (500cc) had a 26 mm manifold inlet. People do screw around enlarging these for a bigger carb so bodged ones must crop up from time to time. Restoring heads properly is specialised and can be expensive. Where I live the few trusted head restorers are always booked out for months! Good Luck. The rear head bolt holes were 5/16" on the early ones and I think they increased to 3/8" but i'm not sure when.I believe the inlet valves got bigger too on the later ones. Years Someone please?
Re: BSA cylinder head identification#26532 06/27/0710:38 am06/27/0710:38 am
thats the head that fits my tbolt a 1964 looking at british onlys catolog it fits from 62-65 in 66 they list a diff number for dual carb head 68-0465 for 65 and back and a 68-0700 66 and forward looks like a single for 66 and newer is a 68-0704 i think this was the same until 71 or so hth aprophet aka david