Nut size please!

[G3L1946]

Hi all,

Can some kind contributor please confirm the nut specifications for the carburettor to cylinder studs please. G3LS 1955.I’ve been advised to use nylon locking nuts with my new Amal carburettor. I was going to use the old nuts with some thread lock but better do as I’m told!

Thanks in anticipation,

Steve

[ajscomboman]

5/16 cycle thread, I'd not waste your money. Never used nyloc before and not had any come loose. If you wish low strength thread compound will do. I also like to fit reduced hex if possible give a bit more spanner clearance.

[G3L1946]

Hi again,

The new carburettor has an O ring whereas the old 376/5 did not. I suppose that as you mustn’t over tighten the nuts with an O ring in place so just added security. Took advice and didn’t bother messing about with trying to service the old carburettor, too many worn parts. Will keep it as a spare or paper weight! Thanks for info and advice. Appreciated.

Steve

[ajscomboman]

Correct, just nip them up enough to hold.

[SPRIDDLER]

Correct, just nip them up enough to hold.

Many years ago we met up with a Surrey member at Dover on her WD Matchless before taking the ferry to a foreign Jampot rally. Although it had run fine for the 80 miles to Dover she couldn't restart it. We found one nut missing from the carb securing studs and the other one about to fall off. It had been only the intake suction keeping it on.

[G3L1946]

Thread lock it is then!

[56G80S]

+1 for Rob's advice. The nyloc may disguise how much the nut is being tightened? Too much and and result is poor seal with face of the new carb distorted. Don't ask how I know.

Aren't the nuts the same as those on the front fork end caps? Someone will know.

JohnnyB

[G3L1946]

Hi JohnnyB,

The installation instructions state that ‘ Nyloc nuts should always be used to mount Amal MK 1 carburettors’. As this applies to MK1 variants, which I believe are concentric carburettors, this requirement may not apply to the 376 or monobloc series. Something to do with bowl position? Decided to just apply a bit of thread lock to the studs and nip up. Carburettor types is not my strongest point!

Steve

[jackstringer]

I'm not a great fan of thread lock, I prefer lockwire. But that is because I dealt with bikes at the Manx GP.

I have never had the nuts on the carb come loose but that maybe becuase I can tighten them sufficiently to avoid them coming loose but not so tight to cause damage.

Nylock are ok, and there are other options available.

[G3L1946]

Hi, I considered using split or helical washers but am concerned that damage to the flange may be caused. I understand, that under vibration, such washers have actually contributed to loosening a nut! If I had a torque setting, that might help but probably going a bit too far. As discussed, nip it up, tadge extra, then that should do it. My original idea of a Nylock nut has been binned.
Lock wire a good option but, unfortunately, not in this scenario.

Steve