The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Billybream on 02.04. 2017 19:03

Title: Mixed guides
Post by: Billybream on 02.04. 2017 19:03

During cylinder head overhaul today discovered the guides were inlet cast iron and exhaust phospher bronze,
these are the originals as fitted by the factory but parts book lists only one type.
Did not take note of this during bike restoration a few years ago.
All guides were worn and need replacing, the exhaust being the worst.
Going to replace with Colsibro from SRM.
Guide removal was easy with head in our oven at 200c for 30 minutes and the use of corrently sized stepped punch and single hammer blow.
Valve seats are ok, but new valves will be also fitted.

Title: Re: Mixed guides
Post by: BSA_54A10 on 03.04. 2017 10:27

Factory only fitted CI to iron heads.
What makes you think it is as it left the factory after 60+ years ?

Title: Re: Mixed guides
Post by: Billybream on 03.04. 2017 10:54

I owned the bike since 1966 and the previous onwner was my foreman who never touched the engine.

Title: Re: Mixed guides
Post by: JulianS on 03.04. 2017 11:06

Looks like the factory changed the guides for light alloy heads from hidural to cast iron in 1957.

Title: Re: Mixed guides
Post by: trevinoz on 03.04. 2017 22:10

That sheet will put the cat amongst the know-alls, Julian.
I have known this for years and always have used cast iron guides in both types of heads.