AJS & Matchless Owners Club

Hi all, I'm newly joined and new to Classic Bikes.
I'm just starting to do a bit of a service and clean-up on my Matchless G2
Brakes need replacing/relining - check
G2 starts great but won't idle, just stutters to a stop. Guy I bought it from said the Carb might need a bit of a tickle.

The Carb is question is an Amal 389, and when taking it apart to clean it and possible blow the gunk out I noticed that the Air Valve, Air Guide and Air Spring is missing?? How odd.

I've managed to find a few classic parts sellers I can get these from, £20 or so BUT this is the problem.

On my bike there is no cable going to it, I imagine there should be something from the throttle??? Carb drawings show a cable?

Update - Is it the choke?? I don't seem to have one

Many Thanks
Mark

Not sure which parts you are referring to having no cable. The throttle slide has a spring and will be cable operated from the throttle twistgrip. I assume you mean the choke slide, guide and spring which are also cable operated by a lever which is separate from the twistgrip. I don't have one on half my bikes, do on the other half. Down in London I rarely use it but if you have been trying to start the bike is this very cold weather not having one would make it run roughly and stall until the engine has warmed up. Just need to keep the throttle running a bit faster until it has.
The only other problem if it is missing may be air leaking in through the hole the cable would have sat in at the top of the carb. This might weaken the mixture a bit so on my bikes where they are missing I have fitted a bit of rubber or cork in the hole.
I am not a lightweight owner but I think the same will hold for lightweights.
My only other thought is the jetting of your carb and whether a 389 is correct for the 250. Someone who knows the lightweights will chip in I am sure.
PS I should have started with welcome to the club

Also be aware that Amal are still around and you can buy new parts from them even new carb.

https://amalcarb.co.uk/monobloc-series/389-series.html

Pic of the parts and how it goes together,
https://amalcarb.co.uk/generic-389-monobloc.html

Plenty of these bikes have worn carbs, I replaced mine to solve a few issues.

Welcome, Mark.
In the 'Carburettor' section of Club Spares the choke slide Pt No 389/062 is listed at £7.69.

See here:

https://www.amoc-parts.com//store/comer ... tegory=143

You haven't said what year it is and it's useful to add the model and year to your Profile.

All the manuals and parts lists are under 'Books' here:

http://archives.jampot.dk/

For a '59 G2 carb it says..........

hi Mark ;
i think you may have wrong carb on the bike, ie its too big , a 389 is the next size bigger to what you need ..

the info SPRIDDLER posted shows a 376/99 carb for a G2 so i expect thats what youll need , its a 1 1/16" bore .

heres link to burlen fuel systems for carb for 58-61 ajs14 matchless g2

https://amalcarb.co.uk/carburettor-for- ... ss-g2.html.

the bits you mention are missing from your carb are the "choke" parts , but they are referred to as air valve . .

not all bikes had "chokes" , some just ran the carb and some may have had a choke flap added to an air filter assembly or in the form of a strangler after the carb [ariel arrow] .

there are a couple of types of choke for the amal carbs , one uses a cable with lever on handlebar and the other uses a push down plunger or a lever plunger that is on top of carb .

basically with the plunger choke levers you push down to lock , start up bike , then flick them off and plunger will come up on the spring pressure .

see below link for choke plunger or choke parts .

https://amalcarb.co.uk/catalogsearch/re ... =376+choke

i dont really know which type of choke you should have but the choice is yours if you want a cable type or plunger type on yours .

amal carbs usually have a number stamped on the top of the flange which denotes what it is , ie 376/99 , and realistically this is what you ought to be using on your bike , but it is possible to build a carb up from another 376 body if you use the correct internal parts according to the amal data .

ive done a fair bit of mucking about with my amal carbs here getting them tuned right on my bikes , you can allways get them sorted in the end , its just going in the right direction thats is you need lol .

hope you sort it out .
ian

.

Ian, depends on the year. 1962 to 1966 bikes had the 389/82.

But going back to the comment made by the OP about what the PO said about the carb. "It might need a tickle". This is a fairly common thing to do. You will find a small brass bar sticking up out of the carb, before you start the bike it's common to press this in and out a few times until your fingers are damp with fuel. Well that is what I do.

Later CSR versions of the lightweights had a 389 fitted as standard.

Some people leave the choke out, as they will start easily when tickled and it is just something to go wrong. It should idle properly once warm.

I would check what jets and slide you have and compare them to what was originally fitted for your model/year. Spriddler has given them for a 1959 G2. Later bikes had different specifications.

There is a screw at the bottom where you can adjust the idle speed by raising the slide.

les ward wrote: ↑Sun Jan 29, 2023 8:41 am Later CSR versions of the lightweights had a 389 fitted as standard

Hence my earlier comment.......

SPRIDDLER wrote: ↑Fri Jan 27, 2023 7:19 pm You haven't said what year it is and it's useful to add the model and year to your Profile