Which model AMALs were on Mark III's ?

A friend of mine has the original set of AMALs from his 75' Mark III that supposedly are like new and offered them to me. They were replaced by a Mikuni years ago and I'd like to put them on my 69' BSA A65 650cc Firebird restoration project that currently has the original 930 Concentrics. The Concentrics are warped and not, IMHO, worth getting re-sleeved and do not have drains on the float bowls.

I'd like to swap out the carbs from the MK III. Any thoughts or info would be appreciated.

Right now I have one of the amal 932's that I took off of my Mk3 on a BSA 441.
It works pretty good.

EDIT: I ported the intake as the original carb was 30mm. and the norton carb is 32mm.

The only way to tell is try it. The 850 Commandos have spray tubes cut away in the front as opposed to 750 Commando AMALs and likely your original BSA AMAL. It may cause a problem on the BSA....or not.

The MK3 carbs can in all likelihood be made to work but I think some fiddling with internals will be needed. The 2mm size increase or the spray tube cut-out on the 932's will probably not be a big issue but the Firebird's 930's slides are a 2 1/2 vs. a 3 1/2 for the Commando. This is a richer slide than that of the Commando carb. The Firebird's main jets are 190 vs. 230 for the Commando. I think you will ultimately need to go up a bit over 190 because airflow through the larger carbs will be a bit slower and a larger jet may be needed for correct A/F ratio, but I think the Commando's 230 will be too big. My guess would be 200-210. That's easier and cheaper than working out the throttle valve number. If all the parts are great in the 932's I'd try the 3 1/2 slides they came with and if the motor has a huge off idle flat spot or practically dies or dies when you quickly blip the throttle you could pop in the 2 1/2's from the original BSA 930's to see if that cures it. Even if those slides are a bit worn you'll get an idea if you're moving in the right direction. Needle position is a crap shoot and I'd probably start in the middle groove. Needles are specific to carbs as far a length and taper is involved and can not be interchanged. By the way, the newer style float bowl with drain plug will fit right up to the older carb so if you should end up sleeving your originals at some time you can upgrade the bowls.

932/42, 932/43
932/43PREM, 932/42PREM

I looked at mine, maybe a range was used?

932R33 and 932L34

One would think, "Big engine, big mainjet', small engine, small mainjet"
But in general, the inverse is true. If no other changes are made other than an increase to engine stroke, bore or both, and jetting is left as it was, correct for the smaller version engine, then the big engine will be jetted too rich.
This comes down to Venturi Effect or Bernoulli's Principle.
The fuel flow thru a given Venturi increases at the square of velocity of the main air flow. If fuel flow thru the Venturi increased in direct proportion to velocity of the main air flow, then the same size jetting would work with both engine sizes. But since flow increases at the square of velocity, the big engine needs a smaller mainjet than the smaller engine, all other things being equal.

Dealing with that right now a 1360 motor that is jetted as a 1200 CC size version of that same motor should be. The 1360 is running somewhat rich.
It's that old V squared thing again.

Glen