The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: rowanbsa on 13.05. 2017 12:18

Title: Piston help
Post by: rowanbsa on 13.05. 2017 12:18
I am looking to get the barrel for my 53 A10 golden flash re bored. It has +40s in currently but the barrel is so worn I've been advised to put in +80s rather than +60s.
Can anyone give me a reputable manufacturer of this size piston? Or have any experience with a certain brand?
The "new" hepolites only go up to +60
Title: Re: Piston help
Post by: ralph on 13.05. 2017 12:55
I am looking to get the barrel for my 53 A10 golden flash re bored. It has +40s in currently but the barrel is so worn I've been advised to put in +80s rather than +60s.

Ayup, you say worn rather than scored - a lot of wear from +40 to a potential +80! From here that is a little difficult to picture. I'd get a second opinion, not only on size, but what could be done to them re the + 80 thing. You're in UK, have a word with SRM - they know their stuff.
Title: Re: Piston help
Post by: rowanbsa on 13.05. 2017 19:35
Sorry, worn/scored yes. I just don't want to have to pay for the re-bore twice if I can help it and get it re-bored to +60 only to find it hasn't cleared it.
Title: Re: Piston help
Post by: BSA500 on 13.05. 2017 19:40
Perhaps a resleeve is a better option more life etc.
Title: Re: Piston help
Post by: bsa-bill on 13.05. 2017 22:02
Quote
Perhaps a resleeve is a better option more life etc.

My thought too BSA500
Title: Re: Piston help
Post by: Black Sheep on 14.05. 2017 06:59
I have yet to see any + .080" pistons (actually, BSA pistons originally went up in 0.5mm increments so that would be + 2mm). A re-sleeve back to standard is what you want.
Title: Re: Piston help
Post by: JulianS on 14.05. 2017 10:04
They are available, BUT, things are getting very thin and remember that the thin flange barrels have been known to crack.

Genuine BSA pistons only went up to + 040, larger sizes were hepolite or other after market manufacturers.

For +080 see below.


http://www.classic-motorcycles.co.uk/cgi-bin/ecom.cgi?Command=ShowProduct&db_pid=5712

Find better barrels, or resleeve as earlier advice.
Title: Re: Piston help
Post by: Scott and Jay on 14.05. 2017 21:49
I have just put in standard pistons and rings from IMD, in UK. They look very good - read the specs.  The proprietor, Adrian Wright was very helpful throughout. He supplied the flanged liners to sleeve back to standard. These won't slip or turn. I have yet to get the engine all back together and report the hoped-for improvement