BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: Mike Farmer on 20 Jun, 2019, 17:07

Title: A65 Heads and Valves
Post by: Mike Farmer on 20 Jun, 2019, 17:07
 :) :) :)

I know about 18 months back we had a long debate about A65 cylinder heads and the change in valve sizes. I can't find it so maybe one of you might help.

When did the heads change? What were the changes to the valve head diameter sizes?

I have a pair of new ones supposedly 68-0156 but the head diameters don't appear to relate to the year/model size.

Your assist appreciated

Mike 8) 8) 8)
Title: Re: A65 Heads and Valves
Post by: A10 JWO on 21 Jun, 2019, 16:27
I remember that the exhaust ports on newer heads were changed to different angles which affected exhaust fitment. Maybe changed the valve sizes as well at the same time. I do remember the thread. I was buying new exhausts from Armours at the time. Mine is a 1971-72. Hope this helps.
Title: Re: A65 Heads and Valves
Post by: Mike Farmer on 21 Jun, 2019, 17:02
 :) :)

HI thanks for that. I seem to have solved the problem.

I was having serious trouble getting the push rods to fit properly. The only way for them to work was with the adjusters fully extended.

However I checked them against another set and they are about 1/4" short. My next set are that much longer and work fine. so job done I think.

I wasn't aware that the push rods came in different lengths. Live and learn

Mike 8) 8) 8)
Title: Re: A65 Heads and Valves
Post by: DerekAnderson8 on 21 Jun, 2019, 18:36
They might be the A50 pushrods you lost last year, they are shorter.

;D
Title: Re: A65 Heads and Valves
Post by: Mike Farmer on 21 Jun, 2019, 19:23
Hi Derek. :) :) :) How are you keeping

Thats quite likely, you certainly have a better memory than me. I wasn't aware that they were different lengths. But then in fairness I have never had them both in bits at the same time. I was just at the point of stripping it to check the valve seats etc.

So anyone care to swap a set of A50 push rods for an A65 set. I'll pay the postage both ways. (I've got two on the go at the mo)

Mike 8) 8) 8)