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Amal monobloc/ concentric

Posted: Sat Jul 26, 2008 9:54 am
by davehutch
Just bought a matchless G2 250cc. It has a amal concentric carb on it.I know it should have a monobloc carb. Its not running very well and i think it is down to the carb. I have cleaned the carb but it is hard to set it up with the air screw. My qestion is can i get it to run properly with a concentric carb. or do i need a monobloc ? If so will any 376 monobloc do ? and what about the numbers after 376/ 99 that is what it say s in the book, but i have seen one on ebay with 376/ 14
will be clad of any advice Thanks Dave

Amal monobloc/ concentric

Posted: Sat Jul 26, 2008 2:11 pm
by paul knapp
Dave, you don't need a Monobloc to have your engine running sweetly, as long as the Concentrics bore, jets and throttle valve (slide) are compatible to your bike.
You can convert almost any 376 carburettor into what you need as long as the bore is ... 1 1/16" I.D.(376 models come in several bore diameters.)
The G2 Monobloc has 1 1/16" bore, 180 main jet, 25 idle jet and a slide with a 3 1/2 cutaway. I could find no referance to a 376/ 14 only a 376/214 which is of a beesa twin, but appears to have the internal parts for your model except for the main jet, which can easily be changed.
Don't rush into buying off ebay till you are sure.

PaulEdited by - paul knapp on 26 Jul 2008 1:17:16 PM

Amal monobloc/ concentric

Posted: Sun Jul 27, 2008 9:54 am
by davehutch
Thanks Paul

Amal monobloc/ concentric

Posted: Sun Jul 27, 2008 11:00 pm
by 56G80S
Sure Paul's got this right, I had the AJS badge 14CSR, 1966.

I've used the concentric on the G80S that was on when I got it 30 years ago.

But it did work a lot better after dismantling, thorough cleaning and re-assembly with new gasket, o-rings, fibre washers and float needle!

Johnny B


Amal monobloc/ concentric

Posted: Sun Jul 27, 2008 11:00 pm
by 56G80S
I got an error message that reply not sent and then there were 2 the same and I can't seem to delete second one, so am trying deleting all of the text in the second one! This message to avoid a blank space.

Johnny B

Edited by - 56G80S on 27 Jul 2008 10:21:08 PMEdited by - 56G80S on 27 Jul 2008 10:22:12 PM

Amal monobloc/ concentric

Posted: Mon Jul 28, 2008 4:33 pm
by davehutch
I have set Timing and valves cleaned carb out. I can now start it when cold first kick every time! But it then runs uneaven and start to miss and back fire, when i try to alter carb on the air screw it cuts out and then after wait for it to go cold to start it again.Any idea ?

Was going to meet the lads at the next local meet which is next wednesday to ask them and introduce myself.

Amal monobloc/ concentric

Posted: Mon Jul 28, 2008 4:52 pm
by paul knapp
How's the spark plug?
Is there a good, continous flow of fuel to the carburettor?

Amal monobloc/ concentric

Posted: Mon Jul 28, 2008 5:31 pm
by davehutch
Spark plug seems fine. and yes flow seems fine.

Amal monobloc/ concentric

Posted: Tue Jul 29, 2008 1:42 pm
by CJU

Amal monobloc/ concentric

Posted: Tue Jul 29, 2008 11:22 pm
by lawrence
Typical of Conway. Once he's started talking you can't stop him