BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: DAVE BRADY on 06 Jan, 2020, 16:11

Title: Oil pump gears - which are best
Post by: DAVE BRADY on 06 Jan, 2020, 16:11
Good afternoon,

Two A10 oil pumps with different gears.  Photo shows the two different tooth profiles with the one on the right looking like there might be more space for oil.  Which one is considered better and when did the changes take place?

Dave.
Title: Re: Oil pump gears - which are best
Post by: JulianS on 06 Jan, 2020, 16:50
The pumps were improved in 1956.

The gears on the right, 15 teeth,  were superseded by the improved pattern, with 14 teeth, on the left.
Title: Re: Oil pump gears - which are best
Post by: DAVE BRADY on 06 Jan, 2020, 16:53
Thanks Julian,

Do you know if the pumping capacity was improved?

Dave.
Title: Re: Oil pump gears - which are best
Post by: JulianS on 06 Jan, 2020, 17:01
Yes pumps with those gears were better.

Service sheet attached.

The late high capacity A65 pumps went down to 11 teeth.
Title: Re: Oil pump gears - which are best
Post by: DAVE BRADY on 06 Jan, 2020, 17:13
Thanks for the info.

So for any one rebuilding, look for a later pump.  I know the A65 pumps culminated in the cast iron body high capacity pump but is there any interchangeability between them?  I suppose the ultimate for an A10 would be late A65 oil pump spec.or perhaps an SRM pump, but then again the A10 pump seems to do a good job if in good condition.

Dave.