Norton 88SS with Single Carburettor

the 376/80 was originally supplied for BSA Gold Flash.  It's almost exactly the same spec as for a  Road Rocket, and similar to the 376/67 (also 1 1/16") as fitted to Norton 600 twins. 

See this web page, kindly supplied by the AJS / Matchless club on Jampot Archives.  It is no longer accessible to non-members, so they may not be pleased with me posting this...

http://archives.jampot.dk/technical/Carburation/Amal_Monobloc__numbers_type_and_use.pdf

376/80 (BSA GF) 1 1/16" bore, 25 pilot, 3 cutaway, 240 main jet, .106 needle, no.3 position

The /76 (for 99) is 1/16" bore, 25 pilot, 3.5 cutaway, 250 main jet, .106 needle, no. 3 position

The /288 (left side for 88SS) is the same spec

/289 (chopped, for right side 88SS) is the same

the /274 and /275 for USA spec 99 SS and 650 are the same.

So, there's a pretty good chance you are in the right ball park, running the standard Norton calibration for the twins, and adjust as necessary to make it run sweetly.  Modern fuels may require altered settings.

Can you give any information about your bike?  What year, which head does it have, and what is the inlet tract diameter at the cylinder head where the manifold bolts on?  My 1955 Model 88 is 15/16" bore at the head, so there is little point going for a larger carburetor.  The 99 used the same head, yet has a 1 1/16" carb.  It may even have exactly the same manifold.....

Paul

88SS was twin carburetter.    (But you could order what you wanted...).  If you must go to a single carb, use exactly the same settings as for the pair. With 500cc, the twin carbs give it much more poke, especially on hills even if you don't want to thrash it on the flat. I'm now at last using twin monoblocs as the factory fitted, and it's running better than ever. For a long time I had one and then two 28mm Concentrics. Ran OK with 3 1/2 slides, 220 main, needle #2 (middle). Didn't like the look of Concentrics. The only really odd noticeable thing is that it needs a handful of throttle to start, especially when warm. Perhaps the pilot screws need closing a bit?

Hi David,   getting the pilot mixture right makes a surprising difference to the starting on my  bike., With it slightly off I can kick away without a peep. The other day I was at Anthonys house and preparing to kick start and  just gently moving the pistons over the top and it burst into life !, of course I nonchalently  made out  this was normal   for my perfectly fettled bike,  HA HA . 

Interesting that the factory sent it with one carb..the first owner must have ordered it that way.  The SS had different cams and pushrods, polished inlets etc.  And 1+1/16" inlet ports (inside the sleeves which could be removed to fit bigger carbs for racing).  Out of curiosity, which cylinder head do you have? The first 100 or so had the pre-downdraft head.

You could run a 62 88SS happily (but slowly) on one 1 1/16 inch AMAL Monobloc carb. If your single carb manifold is the same as a 650 Standard or Deluxe Model which were made for an 1 1/8 inch Monobloc it may be better to fit that carb so the flow of the charge does not step.  If however you have the pre-downdraught cylinder head with the same single carb manifold as the 88 Standard Model then it would have a 1 inch intake at the carb union.  More likely they would have fitted the 99 Standard / DeLuxe Model manifold which had an 1 1/16 inch inlet.  Try not to get a combination where there is a step in the flow.  The 88SS was the best of the early Dominators and is far better with a pair of 1 1/16 inch monoblocs.  Good Luck, Howard