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Author Topic: Amal Monobloc BSA M20  (Read 5810 times)

Offline KeithA

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Amal Monobloc BSA M20
« on: October 22, 2010, 09:36:47 PM »
Hello all; I have a 376 monobloc fitted to my BSAM20. These were standard but only on some of the 50's models. Just wondering, does any-one have jet and needle sizes for this application. can't seem to find much on google.
Thanks Keith :-\
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Offline rivo

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Re: Amal Monobloc BSA M20
« Reply #1 on: October 25, 2010, 03:47:14 PM »
Hi KeithA

I'm far from a carb-expert, but I can google..... So
Will this URL be of any help to you:
http://porklips.org/~mason/moto/amal_specs.html#table1
It states for a BSA M20 of years 1955-1956: Amal 376/021, 1" bore, main=240, needle=0,11, position=3, pilot=30, cutaway=5
And on a BSA M20 of 1957-1959 it states a Amal 376/087 with equal specs

General info on e.g. amal 376: http://www.amalcarb.co.uk

Kind regards,
Rien
(Netherlands)
1950 Norton model 7
(and a never-let-me-down BMW R 75/6, and close-to-a-car 2CV6)
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Kind regards,
Rien (Netherlands)
Domi mdl 7 (1950)
BMW R75/6 (1976)
Citroen 2CV (1988) - it's an air cooled boxer, and almost the same weight as a bike, ain't it?

Offline Goldy

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Re: Amal Monobloc BSA M20
« Reply #2 on: October 25, 2010, 06:48:19 PM »
If you contact Amal in salisbury Wilts they will supply you free of charge their reference catalogue. It states for 1955 Jet block 376/056, main jet 376/100-240, pilot jet 376/100-30, needle jet 376/072-106. All the best
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Offline KeithA

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Re: Amal Monobloc BSA M20
« Reply #3 on: October 26, 2010, 12:28:25 PM »
Thanks very much for your information. It saved me a lot of effort. I could not find the specs on google.
One of my M20's has a 376/04, and it runs great, except it breaks down a bit under prolonged full throttle. I may need to increase the size of the main jet.
My recent M20 restoration, I have fitted a 376/276 monobloc from spare parts, and I cannot get the motor to run unless full choke, and my hand three quarters covering the bellmouth. Any application of the twist grip, and the motor dies instantly. I'm not experienced with the cut-away. I don't want to cut away too much. I want to check all other possibilities first.
I have had to fit the longer spacer between the monobloc and the barrel, so that the float chamber clears the side of the dynamo body. This is a good thing to help with fuel evaporation when hot, plus the monoblocs are a trouble free carb when set up properly. No leaks and trouble free ect.
Now that I have the specs, I can check exactly which parts I have installed, and go from there.
Cheers Keith
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