SU Carburettor

[Klooid]

Hi All,
I have just stripped down my SU Carburettor on my 1962 948cc Moggy, and in re-assembling and when I tighten the screws on the outer suction damper chamber the inner damper unit then does not move freely and doesn’t rest on the bottom unless you touch it to move. However, once I loosen the screws again the damper works quite freely.

Also, I have tried turning the suction chamber round in case it handed, and the stiffness on the inner damper is still the same, and the spring looks okay.

Therefore, is there anything that I need to do to reassemble to have the damper has free movement after tightening the screws?

Thanks.

[Monty-4]

Do I understand correctly you tried rotating the dash pot top? Is the needle properly aligned in the jet, it could be rubbing.

[JOWETTJAVELIN]

You need to centre the jet. This is a very delicate and precise process and must be done with the rest of the carburettor fully assembled ie suction chamber tightened fully. But first of all slacken the large jet securing nut.

[svenedin]

After disassembly the jet will need to be centred. Does the piston move freely without a needle installed? If it does, the jet centring is the issue.

Stephen

[Klooid]

Thanks for the reply and tips, I’ll check the needle alignment, as I didn’t think about that at the time.

[svenedin]

Yes it’s not actually the needle alignment it’s the jet the needle goes into. It’s a fiddly and precise thing to get right. There’s plenty of info on the web about how to do it. When correct the piston should drop with a distinctive metallic clunk. If not done the carb will not function properly.

[Klooid]

Just to say thanks to everyone for your help, as I now centred the needle jet and all is working freely as it should.

[svenedin]

Very much appreciated! So nice when a thread is “closed” with a good outcome. Happy motoring.

Stephen

[JOWETTJAVELIN]

Excellent.