B40 Carb

[Ady]

The carb on my 1961 b40 is going to be replaced with a new one , A monoblock 376 253 is the one that should be fitted but there are non available for 8 to 10 weeks , on the spec sheet it has a internal bore of 11/16s , what is that and would i be able to use a different Amal carb with different specks witch are available .

[chaz]

it should be 1.1/16 not 11/16 diameter, there are a few choices you could try a 280.
I suspect the reason for the delay, apart from covid is that, the bodies are cast in India and machined there when they get an order. once machining done they travel to Salisbury where they are assembled and presumably tested.
they probably keep a few on the shelf, the rest made to order. hence delay.

If I had my catalogue I could look through and find similar numbers for different makes,

[Greenfield]

Hi Ady, if you contact Amal or Hawkshaw or similar they'll tell you which spec you need. Yes, its a monobloc 376 which is 1 and 1/16" bore. Have a think about fitting a premier concentric instead. I'm sure that they'll be able to advise which setup you'll need. It'll look different on the outside, but you'll have all the benefits on an alcohol proof concentric. I wish I'd have gone this way when I renewed mine a couple of years ago.

[Ady]

Thanks guys , i think it might be best to check out the concentric one .

[Mike40M]

Ady, if you go the for a Concentric, please tell what you decided.
Thinking of going that route. 1+1/16 is circa 27mm which is between the Concentric sizes. Either a 626 which Burlen states was fitted to the Australian WD B40 or a 928. I believe the smaller one could perform a bit better plodding around and the bigger could give better top end performance. Thinking of carb and head diameter matching too.

[Ady]

Ok , the Concentric is on its way not sure which one as i asked burlen to send the one that would work with my bike , soon as its running right i will report back .

[hoogerbooger]

Hi Ady

If poss can you let us know which Concentric/Set up Burlen provide.....and how it goes.

Useful to know.

Hope it works out of the box for you.

[Ady]

The new carb arrived and was promptly fitted , Started the bike , engine ran but was running rich adjusted air screw and it ran for a short time and stopped . Tried to restart but it wouldn't  go  . The bike had similar starting problems before the carb swop , could the condenser be at fault here  or something else that brakes down until its cooled off .