The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 1946-1950 => Topic started by: barry2 on 07.02. 2019 00:51

Title: Was there an A10 long stroke engine
Post by: barry2 on 07.02. 2019 00:51

Hi mates
Was there a long stroke BSA A10 engine? and/or was there a close coupled A10? thanks a lot
Barry

Title: Re: Was there an A10 long stroke engine
Post by: muskrat on 07.02. 2019 01:38

G'day Barry.
Not from the factory that I know of.
If you put an A10 crank into an A65 = a long stroke A65 = 742cc.
Cheers

Title: Re: Was there an A10 long stroke engine
Post by: barry2 on 07.02. 2019 01:48

Hi Mates
I was refering to early engines ie a close coupled A10 that looked a long stroke A7
Barry

Title: Re: Was there an A10 long stroke engine
Post by: muskrat on 07.02. 2019 06:05

G'day Barry.
The only "long stroke" was the early A7 500 with a stroke of 82mm from 47 to 50. Then the AA7 had a shorter stroke of 72.6mm. The A10 started in 50 (semi unit till 56, S/a started in 54) and had a stroke of 84mm till the end in 63. No "long stroke" A10 for public sales but you never know what lurked in the race department.
Cheers

Title: Re: Was there an A10 long stroke engine
Post by: barry2 on 07.02. 2019 07:35

Hi Mates
Thanks for that, was thinking, the short A7 and A10 had the same engine/crank but w/ diff bore
and all the close coupled had same crank w/ diff bore
Barry

Title: Re: Was there an A10 long stroke engine
Post by: muskrat on 07.02. 2019 08:07

The A50 and A65 share the same stroke of 74mm. A50 bore is 65.5mm, A65 bore is 75mm.
Cheers

Title: Re: Was there an A10 long stroke engine
Post by: Swarfcut on 07.02. 2019 09:08

 Anyone tried an A7 crank, small journal A10 rods and pistons in a cut down A10 barrel......if only to avoid the expense of repairing those missing  top fins? Would give a capacity of just under 600cc and give an almost over square stroke/bore ratio. Plus more torque than a standard A7 (bigger piston crown surface area).

   Barry.... There is a picture of a twin engined bike, a homebrew special, in Roy Bacon's "BSA Twins and Triples"...Comes in Chapter 10......"Oddments."

 Swarfy.

 

Title: Re: Was there an A10 long stroke engine
Post by: Klaus on 07.02. 2019 09:28

Hy Swarfi,

I do the other way, A65 crank and 6" rod in A7 case and a shortend thickflange A10 barrel whos missing their top fin. Pistons are JP 0894 STD with 72 bore.

cheers Klaus

Title: Re: Was there an A10 long stroke engine
Post by: Swarfcut on 07.02. 2019 09:40

Klaus  That is very clever. A big journal crank, better rods with a nice big piston pin. Short stroke/ bigger bore. Looks just like a standard A7.  A wolf in sheep's clothing.  NICE.

 Swarfy.

Title: Re: Was there an A10 long stroke engine
Post by: Klaus on 07.02. 2019 13:44

Yes, thats the plan in combination with a megacycle race cam and a twincarbhead, I will devil the big bikes up to 1000cc at the racetrack.

But it is a lot of work, and will never do again. I had the parts, the damaged barrel, a cheap a65 crank, and the cases. The hadest thing was sort it out the pistons. The SRM rods have no bush, so I only can fit a 3/4 inch pin.

cheers Klaus