Hello to all.
I have a question concerning the union nut for the carb 276c1 / b there are two models, one long and one short which is used in carb276c1 / b?
What happens if you install the wrong union nut? (for example if it was just short the correct one and I'm going to mount that long.
Thanks in advance
Mark

It alters the fuel level and makes it richer or leaner.

email (option): horror@blueyonder.co.uk

There are at least 3 different sizes. Generally for side valves the shortest available is used and same goes for an M20.

I have been riding around not knowing I had the wrong one and I just couldn't get my mixture ok.

Henk

email (option): ahum@quicknet.nl

I agree for an M20 you need the shorter one. I often see M20 bikes for sale on Ebay with the longer nut or with an angled bowl which also upsets the running. A lot of guys think a bowl is a bowl and any Amal carby base nut will do.

This is mine when first bought a few years ago



this is how I altered a refurbised carb ( 276 )



just using an oil pipe nut to get the idea of the joint, I then soldered up a new copper pipe to another joint at the opposite side of the tank.

now running rich, maybe this is part of the problem.
I was going to drop down a jet size. Maybe need to change the bowl back to the old one.

Paul C

email (option): bsa945@btinternet.com

Side-valves are were traditionally fitted with short nuts (and therefore a higher fuel level) as their poorer gas flow and less efficient induction otherwise caused a poor response to the sudden opening of the throttle.

However, like you, I struggled with richness that I couldn't otherwise cure on my 16H and have ended up using a long nut. I replaced the float chamber and needle with NOS to original spec and it didn't seem to help. I know of several others who have also resorted to longer nuts. This is not out of ignorance or a desire to fiddle, but a way of dealing with a very definite problem.

I do wonder if the density of modern fuels is a problem and if our heavy brass floats are a bit borderline nowadays. Although a static check with the cap off shows no problems, this might not be the case on the road. Perhaps the next step would be to try a modern plastic float.