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BSA cylinder head identification #26528
06/24/07 11:23 pm
06/24/07 11:23 pm
Joined: Apr 2004
Posts: 89
Front Royal, VA
J
John M Offline OP
BritBike Forum member
John M  Offline OP
BritBike Forum member
J

Joined: Apr 2004
Posts: 89
Front Royal, VA
Greetings, all!

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.

Thanks!

John M.

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?


latin81@comcast.net
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Re: BSA cylinder head identification #26529
06/26/07 2:23 am
06/26/07 2:23 am
Joined: Mar 2005
Posts: 731
Asheville, North Carolina
C
ca7a Offline
BritBike Forum member
ca7a  Offline
BritBike Forum member
C

Joined: Mar 2005
Posts: 731
Asheville, North Carolina
Sounds like it's a unit BSA component, although it's most likely not a single cylinder head. Post a pic and let's have a look.

Re: BSA cylinder head identification #26530
06/26/07 3:47 pm
06/26/07 3:47 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

BritBike Forum member
Alex  Offline

BritBike Forum member

Joined: Sep 2002
Posts: 7,813
Seattle
John, with a set of calipers and factory shop manuals you can figure out what size valves you need. The guides for all the earlier heads are the same. The BSC threads went up to '68, I believe.


A smattering:
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Re: BSA cylinder head identification #26531
06/27/07 10:06 am
06/27/07 10:06 am
Joined: Jun 2007
Posts: 172
Australia
G
gollywog Offline
BritBike Forum member
gollywog  Offline
BritBike Forum member
G

Joined: Jun 2007
Posts: 172
Australia
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?


signiture
Re: BSA cylinder head identification #26532
06/27/07 10:38 am
06/27/07 10:38 am
Joined: Oct 2001
Posts: 633
Chesapeake Virginia
aprophet Offline
BritBike Forum member
aprophet  Offline
BritBike Forum member

Joined: Oct 2001
Posts: 633
Chesapeake Virginia
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


1964 A65C Rocket (Jeanie)
1971 T25SS
1971 A65T BSA (Lucile)
1965 A65D Lightning Rocket

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