1954 NH 350 Carburettor

[robj_b]

Hi all

Around 6 months ago I picked up a 1954 NH 350 that I have slowly been getting ready to ride, it does seem to have a few parts that may have come from other bikes, I took it for a bit of a shake down today and all seemed generally good, starts first kick and although I'm not expecting much in the way of power I am wondering if it might be let down by the carburettor thats fitted. It has an Amal 375 currently fitted which im guessing is not the original, would I benefit from upgrading this to a 376 or should I stick with what I have.

Thanks in advance.

Robert

[will_curry]

According to Waller the 1954 NH would have had an Amal Standard 276 carburettor fitted but I don't know
what size. 1955 and on NHs had an Amal 376/008 carburettor with a 1" bore.

Your 375 will be less than 1" so may well be restricting the larger throttle openings.

I'd look for either the 'proper' 276 or a suitable 376.

[robj_b]

Thank you for the quick response, I might look out for a suitable 376 there do seem to be more available than the 276.

[simon.holyfield]

Thank you for the quick response, I might look out for a suitable 376 there do seem to be more available than the 276.

You can buy a new 276 from Burlen or Hitchcock's...

[robj_b]

Thank you Simes, I was kind of hoping to find a decent used one to save a little.

[tony.barnett]

Depends on the choke size of your 375 as to whether a change to a 276 or 376 would make any difference. If the 375 choke is less than 1/8" different to a 276/376 I doubt it'd make a lot of difference.

There are plenty of used 276 carbs for sale out there, at autojumbles and on ebay. Even on here occasionally. All of the tuning parts can be obtained. Just be careful regarding the float chamber angle which would need to be right for an NH (I don't know what it is but someone will...).

Or buy a 376 monobloc instead. Up to you.

[robj_b]

Hi Tony

I currently have the 375/31 which according to the Amal website has a 7/8" bore, if you feel 1/8" won't make much difference then I may just stick with this for the moment.

[tony.barnett]

Actually I was thinking more like 1/16 rather than 1/8, but if it works then leave it for now then look for a bigger carb at your leisure.

[robj_b]

Ah ok, what about going the other way is it possible to fit a carb with a 1 and 1/16" bore or is it just too big?

[nevhunter]

IF you are prepared to tune it you will get away with it. A larger than normal carb. Bore has less SUCK ( velocity) at WOT so will need a larger Main Jet. That's easy to swap. Nev