Bsa Alternator, Crankshaft type.

[Harryc208]

Engine cases are CA7 SS 8223  which I think is 1961?

The rest of the engine parts will vary with age.

Its got the twin carb Alloy head.

Ok so to fit the a65 crank,

Turn a sleave to adopt the A7 bearing.
Get hold of some alternator chaincases.

Would I fit a7 pistons, turn a smaller ID bushing to replace the small end bushing of the a65 conrods?

[muskrat]

 Yep, I forgot A7 pins are 11/16", A10 & 65 are 3/4".
Finding the primary covers will be the hard part. If you know a good alloy welder and machinist you could convert the originals. I saw a pic of a home made one not long back.
A7's only have thin flange barrels so go easy on the compression, say 8.5:1, 9:1 max. I've broke a few of those as well.
Cheers

[Harryc208]

Already considered adapting the chain case,

Could cut a hole the size of the stator in the outer chain case, turn a ring to house the stator and tig weld it onto the case.

Among the parts I have, there is some bored out cylinders to take Bonneville pistons. The trouble is on the a7 crank and rods they don't reach the top of the cylinders, I?m wondering how far they would go up with the a65 crank and rods. Time permitting tomorrow I may have a mock up and see.

[muskrat]

Fitting, Fitting I know. I had 67mm trident pistons on 2.5mm shortened A10 rods, but they were sml journal.
The crank will only push them up by 0.6mm. I'd sleeve the cylinders back to std and use A7 pistons.
Cheers

[Harryc208]

Now I have thought about it, when I looked at the bonneville conversion before the thing I didnt like was that the barrels overlapped the edge of the head.
That engine in question was partly stripped when I got it, the head was off, so I think it had blown the head gasket.

[muskrat]

 So if the A7 barrels have been bored out to take 71mm bonny slugs they wouldn't be strong enough to hold a fart let alone decent cr. Sleeve it back and std A7 pistons with the extra stroke will give a decent cr result. To play around with the cr use different thickness head gaskets. Lani at copper gaskets can make them in any thickness and bore size. http://www.coppergaskets.us/MCG.html
Cheers

[Harryc208]

Thats a point I hadn't even thought about, Il have them sleeved.

On the point of strength, In one post didn't you mention a through bolting system? Would that be applicable here?

[muskrat]

If I tell you I'll have to kill you !
Depends on if you want to race it. I was running 13:1 cr on methanol. After breaking a few barrels I worked out the through bolt system. Then it broke a couple of small journal A7 cranks (no large journal for A7). Just moved the weakest link. Hence the idea of the A65 crank. Stopped racing so shelved the crank. I still use the through bolt on the '51 and '57 cafe because I can 
 Keep yours at 9 or less and should be OK.
Cheers
 PS, once done for through bolting the head and barrels are that way for life, the cases can revert to std.

[Harryc208]

I wont be racing, and 13:1 on the fuel we have here would send most engines to mars.

Il try and have barrels sleaved soon, in the meanwhile il have a look at a sleave for the drive side bearing.

[muskrat]

I was telling a friend (poor bugga has only 12 bikes, 1 is a ABSAF 600 Goldie) and he thinks the late B33 alternator covers will fit, or made to.
Cheers

[Harryc208]

After contacting ABSAF, been quoted ? 495,00 plus vat for a set of primary cases unpolished.

A little out of my price range, so I think il end up making my own.

[Flatboy 1950]

Hi , I have a set of Alternator chain cases for a twin , but I am in South Africa & the postage usually kills any deal !!

Regards , Flatboy.

[Harryc208]

You have PM flatboy!