Hi folks,
Another area that has me a bit puzzled...

Have I got the wrong carb on my bike?

https://scontent-lhr3-1.xx.fbcdn.net/hphotos-xpt1/t31.0-8/11164633_933128153414654_104681316264725714_o.jpg

email (option): fozzie001@hotmail.com

Hello Ian F.

Yes, your carb is newer, looks like one of the 376 series of Amal,
(Like the newer BSA models,but this is a "left side" carb, and appears bigger than the 1")

With a cafe-racer heat insulator in addition to the original one,
And much longer carb studs than the original.

The correct model should be Amal 276C/1B.

Also, if it matters to you,
The voltage regulator should be mounted directly on the rear mudguard,
Without that 90 deg' bracket.

Regards,
Noam.

email (option): noam10@gmail.com

it looks like an amal mono block possible from a twin carb set up being that the float chamber is on the inside from post war bike be carful tickling it as the petrol will dribble into the magneto

email (option): roger.beck@node6.com

You may have an M21 barrel...These are the same casting as an M20 barrel but measure 1 1/16" at the port..not 1" as for the M20...

This makes no practical difference to the running of the bike but the M21 used longer carb mounting studs and a cast aluminium spacer between the carb and barrel...

You should have a 1/4" tufnol insulating spacer, gaskets, shorter studs and the 276 carb as detailed by Noam...Ian

Thanks guys - now I know what it is, but also, it seems the carb has been with the bike for a long time (judging by the patina), and so, as it works just fine, I have no plans to get rid of it just now, (and besides, I like the pretty flared air intake) - Also, I see that it is stamped with the date 3/6/1940 :-) I will gladly change the carb if one of the "proper" carbs lands in my lap ;-) As for the angled bracket on the regulator - I thought it looked a bit suspect, but I can also see why it was put there in the first place, it seems to make access of the connections a bit easier... Might take that off though - will need to look at it in the daylight again :-)

email (option): fozzie001@hotmail.com

Hi Ian F,

I am not sure about the date, as "Amal" started fitting the 376 'Monobloc' from 1955,
As far as I know..

This "Flared intake" is a "Velocity stack" which also available for the 276,
And suppose to improve the intake airflow.

Of course, there is no problem using this carb, which is correct for later models.

Noam.

email (option): noam10@gmail.com

Yep..The monobloc was introduced for 1955 so whatever is stamped on the carb it's not a date of manufacture...

The finned inlet spacer was an aftermarket 'go faster goodie'...They used to be manufactured by John Tickle for fitment to café racers....I think Norton Commandos might have had them as well but that might just be my memory fooling me (again)....

Now available again in 'replica' with the resurgence of interest in that style of bike...

Like wise the carb 'bellmouth' intake...

I would guess the whole carb, 'bellmouth' intake and finned spacer set up might have been 'lifted' from an A10 or similar years back...Ian

If the bike is running well enough, why not leave it on?

There is a question with these old bikes, whether to leave 'period' mods as part of the history of the bike?

Unless you go for a full nut/bolt/rivet-count build from ground up - to produce something 'totally original - as it left the factory' ....

I think I'd prefer to see something running rather than something in the shed - waiting for the 'correct bit' to turn up.

NEW 276 carbs are available for these bikes direct from Burley Fuel - put AMAL UK in your search engine and they will come up.
Relatively expensive (I think something like £260) - but at least you will have something that doesn't flood every 5 mins, will tick-over smoothly and is set up for your bike.

Hi guys,
Thanks for the replies :-)
My current plan is to leave the bike "as is" for the time being. This is for two reasons... 1) I don't really seek the "as new" look for the bike, but much prefer the "in service use" look, complete with gremlins and modifications... (I was an Army Vehicle Specialist for 15 years... Apart from brand new vehicles from the factory, we never got "new" vehicles back to the depot, they all had some idiosyncrasies attached to them, even the bikes, which I was in charge of for some time) and 2) My priority is to get the bike on the road and out on display for this summers WW2 show season.
My bike was demobbed in May 1955, so it is feasible that the carb may have been fitted prior to it leaving the Army? We had BSA 350's when I was in the mob, and when they went to disposals, they had all sorts of wierd modifications on them :-) I do recall that we had a few Triumph 500 Speed Twins in storage too, but no one touched them & they just sat creaking and gathering dust in a corner till I left.

I digress... I got my WM20 running today, but that has opened up a whole pile of different problems to be dealt with...

Just been looking on "EvilBay" at the carb availabilty of the 276 & got even more bogged down when I saw so many different references to what appears (to a novice like me) all to be the same carb :-(

276/424R
276AX/1AT
276BL/1A
276AW/1BB
276/012
76/130R(276/DZ/1B)
276AE / 1BE
276/EL/1D
276AV/1ED

And then I read somewhere else that it's the 276C/1B that I need :-/

email (option): fozzie001@hotmail.com

Ian the 276 is the carb model for a WM20 (the 76 is the earlier version so you can forget those) The other numbers (confusing as they are) are just to indicate the way the carb is set up. jets, needle, slide, float bowl angle, fuel pipe spigot etc. Basically any 276 carb body can be made into an M20 carb by just fitting the right bits.

And yes the correct carb is a 276C/1B

email (option): ronpier@talk21.com

Ian

As the local carb expert (I truly don't want to be...but I have a vast amount of Mikuni/Amal/PWK jetting) my recommendation is to get her running and see how she goes.
If it starts, doesn't flood and doesn't blow out lots of black smoke, then run it!

Then grit your teeth and buy a brand new carb from AMAL (amalcarb.co.uk)
While on the amal website - 'buy' the "AMAL Catalogue - 1940 On" and "AMAL Pre War Supplement" - they are actually free, but you have to pay for P&P.
This will give you the original jetting for your bike.

If you insist on going down the S/H route, then get a picture of the correct carb. - again from the Anmal website, theres also many downloads to look at.

The 276 is simply the 'body casting' size/type - the bore can be anything from 7/8-11/16" or something like - the experts on this site will tell you what the correct bore is for your bike - at a guess 1" or 7/8".
This is the first thing to look for/buy - you can measure the bore size with some calipers and rule - the correct size in measured across slide-block.

You also need to find the correct fitting - spigot (16H) or flange mount (yours) - bear in mind the flange fitting carbs ALWAYS have a warped (not flat) flange.

The next thing is the correct float chamber - there are top fuel in and bottom fuel in - doesn't really matter which from a running point of view, but the top-feed does seems to want to float more easily than the bottom feed.
What DOES MATTER - is the angle of the float chamber, when it bolts to the carb.
I think on M20/21's the f/chamber is @ 90deg to the line of the carb - in Amal speak this is 0deg down draft - there are countless other angles.

When you have the main component's - you need to sort the jetting.
Bearing in mind that the needle slide is something like £51 new and most s/h ones are ............... buggered/worn/'crushed' etc.
The slide block can be ............... buggered/twisted/crushed, not certain of that price but it will be expensive
I would definitely recommend an overhaul kit containing needle/needle jet/main-jet/pilot jet - £22, but good value.

Etc. etc - the cost mounts up, you can EASILY spend £100 and the carb is still +50 years old and has been stripped/assembled in a vice (hence all the crushing) - so £280 (just checked price) for a brand new carb isn't so bad.

At least when the bike starts acting up, you can ignore carb problems (?)

PS - I personally have never bought a new one, but have fitted three so far to friends bikes and they have been transformed.

email (option): ginantonik@tiscali.co.uk

I fitted a new one to my M20/21/720.. ...I checked the base settings, bolted it on, spent a short while fine tuning it and basically haven't looked at it again apart from stripping, cleaning and reassembling it the last time I did some work on the top half of my engine...

I bought it not long after Amal started remaking them...15? years ago...

Definitely recommended and a lot less trouble than used or reconditioned carbs I have had...Ian

Me too. I bought a new one when I fitted an M21 crank and piston to upgrade to 600cc. An M20 has a 1" carb and 1 1/16" for an M21. My M20 barrel already had the inlet port at 1 1/16"+ so I didn't have to open the port at all. The few others I've looked at were all also at 1 1/16". I think the M20/21 barrels are the same part number, so I guess at some point they just made them to use on either model? Ron

email (option): ronpier@talk21.com

Thanks folks for your valued and knowledgeable information.
I will get her running first and see what's what after that - the new carb could be a winter project later down the line though :-)
Best wishes
Ian

email (option): fozzie001@hotmail.com

On sunday, on the Bamburgh run there was civvy g/fork m20/21 + sidecar, happily chuffing about - it was fitted with a mk1 Concentric carb (a truly terrible thing) started first/second kick and everyone comment on how nice the outfit was .... no mention of the wrong carb.

And these were VMCC members as well .......

Have fun and get the old girl out there

email (option): ginantonik@tiscali.co.uk