650SS 930 Amal fitting confusion

If you look in the later edition of the Norton Handbook the P106P there is a chapter on the Amal Concentric carburettor.

The choke size is 30mm and they used the Amal 930's

Main jet with air cleaner is 260, and with out air cleaner 280.

Pilot jet is 25cc, Throttle slide is a No 3, Needle jet is .107 and the needle position is Central notch in the slid.

If you look in the Master Parts List of 1966-1967-1967, on page 9 then it list all that you will need to know.

Tom.....your carb intake spacers are too thin. You really need the 1" (25mm) size spacers to get the best performance out of these carbs. They will also fit on the studs better. I think the part number is 23872 but do check this out.

Previously tom_steele wrote:

Hi Everyone,

hope you are well, I'm struggling to fit my new premier amal carbs

got some shorter inlet manifolds and the studs and allen bolts that are meant to be for them

also got the original inlet manifolds that were off the 376 carbs,

question is which set up is right

tom..

you need to use the 1" spacers as phil suggested with a tufnal up against the head. thats the set up i have and with the standard studs should be ok.

tony.

put some pictures up

option one

slim gasket, tufnol, slim gasket, tufnol, slim gaskets, manifold then carb

option 2

get some longer studs and use the original mono block inlet manifolds

option 3 cut the studs an the allen bolts down

then fit gasket, tufnol, gasket

help please haha confused and not much in the haynes manual or books

Thanks in advance,

Tom

Tom. The original inlet spacers fitted with 376 monoblocs will have a smaller bore, 1 1/16", than the 930 concentrics which you are planning to fit. You will have a mis-match of parts, and will need to open them out to 30mm; 1 3/16". You will then need to remove the steel sleeves in the head, and blend the ports in to match.

I assume this has not already been done, as you have the 376 monoblocs at present. You may have been better off getting 26mm concentrics, or maybe 27mm with a little blending of the inlet spacers to suit. The bigger 30mm carbs may give you a few more revs at the top-end, whilst sacrificing mid-range.

Hello Tom - I had a late 650SS (67/68) that had two concentrics fitted as new. It also had the shorter inlet manifolds with balance pipes and no air filter (optional fit). It also had the twin coil set-up with the capacitor in parallel with the battery. It ran very well without hesitation or misfires. It wasn't as quick as the early ones but it was or appeared smoother. I also had an Atlas from a similar year and it was similarly configured with concentrics. I seem to remember a story about the spray tubes and needles being different to other configurations. Phil may enlighten us ?? Cheers - safe riding, Howard

Howard. Bear in mind the later 650 to which you refer had a different head, different ports, different carbs, different carb spacers, different rocker geometry, etc from the earlier ones. It can lead to a classic mis-match of parts from different years not working as well as one may hope. Phil will remind us that he once fitted bigger carbs that made the bike slower.....