M21 - how to switch to Monobloc?

[berniej]

The original carb on my '49 M21 engine has become so unreliably leaky that it's becoming a danger.
When the needle doesn't seal or it leaks elsewhere the fuel drips come rather close to the hot exhaust.

I think I should switch to a monobloc for peace of mind.

Can anyone provide the right spec please and also - if anyone has one for sale - please let me know.

Thanks,
Bernie

[Allan G]

Hi Bernie.

Taken from the Amal catalogue.

M21 Home and Export settings, for 1955-1960

Carb number 376/88 1957-1960 (or 376/23 - 1955-1956 - settings are all the same, so don't know what changed)
Bore 1 1/16
Main Jet: 250
Pilot Jet: 30
Needle Jet: 106
needle position: 2
Throttle Valve: 376/0605 (#5 cutaway for 376 carb)



Interestingly, the AA order model bikes, stuck with a 276 right till the end of production - god only knows why!!

[berniej]

Great - many thanks Allan!

[V500]

Phone Burlen, Hitchcocks or Surrey Cycles, tell them what it's for, pay them some money and they do the rest.
I'd go for an Amal premier personally.

[maddogmargetts@yahoo.co.u]

Confirming the specs from Allen G. Your air screw at 1 and a half turns out. I got a brand new 276 and it leaked like a colander so got the 376 which worked immediately with hardly any tuning needed.