Carb question.

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
Locked
ColourNcoat
Posts: 140
Joined: Thu Oct 22, 2020 8:07 pm
Location: Monmouthshire UK

Carb question.

Post by ColourNcoat »

Hi All, She is finally running but it is definitely running rich.
The carb is a 786 which I believe is not standard.
Would anyone know which jets etc were/are fitted to it to run on the 1965 csr just to give me something to go on.
Many thanks as always
Roger.
User avatar
Samuel
Member
Posts: 1067
Joined: Tue Sep 09, 2003 1:00 am
Location: Somerset UK

Re: Carb question.

Post by Samuel »

According to Burlen Fuel systems the correct spec is:-

Carburettor Specification: 389/82
Make: Matchless
Model: G2CSR
Engine Size: 248cc
Carb Type: 389 Monobloc
Year: 1962 to 1966
Number of Carbs: 1
Needle Position: 3
Internal Bore: 1 1/8in

See http://amalcarb.co.uk/carbspec/carburet ... s/id/6642/
Sam
User avatar
Rob Harknett
Member
Posts: 11236
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Carb question.

Post by Rob Harknett »

ColourNcoat
Posts: 140
Joined: Thu Oct 22, 2020 8:07 pm
Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

Sorry folks, its a 376 and after reading I knew the standard carb was a 389 but is it possible to run it on the 376?
I just want to run it in hopefully on the 376 until I can get a 389.
Many thanks for both replies they are really appreciated.
Regards Roger.
Last edited by ColourNcoat on Thu Feb 11, 2021 7:00 pm, edited 1 time in total.
User avatar
clanger9
Posts: 1165
Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: Carb question.

Post by clanger9 »

Is your 376 a 1 1/8" bore? It's essential that there's no step on the inlet manifold, otherwise it'll never run right...
1989 Moto Morini Dart 350
1993 Ducati 750SS
ColourNcoat
Posts: 140
Joined: Thu Oct 22, 2020 8:07 pm
Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

clanger9 wrote:Is your 376 a 1 1/8" bore? It's essential that there's no step on the inlet manifold, otherwise it'll never run right...
unfortunately I will have to measure it tomorrow. There weren't any other numbers to my recollection.
Shall have to take it back off tomorrow.
Many thanks
Roger
User avatar
clanger9
Posts: 1165
Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: Carb question.

Post by clanger9 »

I think 376 carbs only go up to 1 1/16" (?), so if there's a step then that's probably why it seems to run rich.
Here's a great article that explains why: http://archives.jampot.dk/technical/General_technical_topics/Induction_port_obstructions__(by_George_Templin).pdf
1989 Moto Morini Dart 350
1993 Ducati 750SS
ColourNcoat
Posts: 140
Joined: Thu Oct 22, 2020 8:07 pm
Location: Monmouthshire UK

Re: Carb question.

Post by ColourNcoat »

clanger9 wrote:I think 376 carbs only go up to 1 1/16" (?), so if there's a step then that's probably why it seems to run rich.
Here's a great article that explains why: http://archives.jampot.dk/technical/General_technical_topics/Induction_port_obstructions__(by_George_Templin).pdf
Unfortunately there is an error 404
Roger
Working now sorry
56G80S
Member
Posts: 3353
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: Carb question.

Post by 56G80S »

The articles is fascinating and I will be taking the oportunity to tidy this area up. I've known for a while that the spacer size didn't accurately match the head or the carb.

It's not much but......................

Johnny B
User avatar
clanger9
Posts: 1165
Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: Carb question.

Post by clanger9 »

Good article, isn't it? It doesn't take much of a lip to cause havoc...
1989 Moto Morini Dart 350
1993 Ducati 750SS
Locked