BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: Tjwood on 04 Sep, 2024, 20:43

Title: Need pistons for 1968 A65 Thunderbolt
Post by: Tjwood on 04 Sep, 2024, 20:43
Hi. I'm rebuilding a 1968 A65 engine for a Thunderbolt. I need new pistons as I'm having to get a rebores barrel. I'd like low compression ones if possible but that might be difficult to achieve as most A65 pistons seem to be 'high dome' ones. I'm really unsure about which brand of pistons to get. I've heard bad things about JP (poor weight match) and some rumours that new Hepolites have awful rings so I'm a bit stumped. I've tried to find GPM (Gandini) pistons but they don't seem to cover late 60s A65 engines. Any advice would be gratefully accepted.
Regards
Tony
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: cdsdorset2 on 04 Sep, 2024, 22:41
Have you checked with Burton bike bits.
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: Tjwood on 05 Sep, 2024, 12:48
Thanks cdsdorset2, I'll give them a call
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: Dibble on 09 Sep, 2024, 08:26
I seem to remember SRM stocked GPM at one time! Good luck.
Dave
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: TERRY WOOD on 09 Sep, 2024, 14:16
Do you know what size you need to go to. I have a pair of used low compression i will check the size
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: Mike Farmer on 11 Sep, 2024, 11:33
 :) :) :)

Hi. I have a pair of used Std low comp pistons about 5thou worn. If you are reboring/relining you could have your bores done to size. Just a thought.

Mike 8) 8) 8)
Title: Re: Need pistons for 1968 A65 Thunderbolt
Post by: Tjwood on 18 Sep, 2024, 20:14
Thanks guys. It looks like I'm going to have to go for +20 as one cylinder bore has a small rust patch that won't clean up.
Regards
Tony