B31 carburetor clean

[rustyboots]

Hi all.
just doing a carby clean for the first time since ownership and need to ask a couple of questions.
My terminology / parts ID may be incorrect, Be Gentle with me.Hoping the pics help.

Background!

Bike is a 1960 ish B31 bitsa, fitted with an Amal 376/58 carb,
main jet looks like 106,
pilot jet is 25.
not found any blockages so far.
None of the butchery is my doing by the way

Q1.Does the main jet holder require any sealer? came off dry but was ridiculously tight.

Q2. should there be a gasket under the filter within the inlet banjo?
TIA

[limeyrob]

Little nylon strainer under banjo - no fibre washer as the plastic makes the seal.
Jet holder - yes there is a fibre washer.  Easy enough to get, may come in a kit with the tiny one on the pilot jet cap.  These often split then go missing.
Brass nut on the main jet, no this seals on the taper, and yes these can get really stuck.
Your carb may or may not have an o ring on the face where it makes to the engine. Check the face for flatness, over tightening the two nuts bends the carb quite easily.  Flat it with some fine emery on a plate of glass.  It looks OK in your first photo.

[rustyboots]

many thanks for the info, i do have a gasket set from feked, still looking for a place for the paper one and a red fibre one.probably haven't stripped it back enough yet.

[Derek996]

I think 106 jet is the needle jet. The main jet should be a 260 for the Monobloc.

[rustyboots]

UPDATE ON INFO

 
 I have posted wrong info for you guys to work on

Needle jet is 106
main jet is 180
pilot jet is 25

[Derek996]

That main jet looks a bit small. I have attached a pic the 1955 carb settings for the B series models. The jetting remained the same over the years. You can see that for a B31 with a 376 Monobloc the main jet should be a 260. If an air filter is fitted it might be a size or two smaller - 250 or 240.

[rustyboots]

Hi Derek, thanks for the info, i'm getting more confused by the minute, google tells me this.
The Amal 376/58 is a 376 series Monobloc carburettor configured specifically for AJS 30 Twin and Matchless G11 Twin motorcycles, produced between 1955 and 1957.

only took it off to give it a clean and check it out, as bike would not rev after an 8 week lay up.
gasket kit from feked for the 376 went on fine, but have no idea whatsoever regarding jets etc. the needle is marked with a C, again google tells me that is a standard fitting.
with the bike being a bitsa and no history its a big learning curve.
do you think i should throw in a larger main jet anyway to see how it goes?
No air filter fitted, only an alloy trumpet which i cannot get off

[neil1964]

Hi Derek, thanks for the info, i'm getting more confused by the minute, google tells me this.
The Amal 376/58 is a 376 series Monobloc carburettor configured specifically for AJS 30 Twin and Matchless G11 Twin motorcycles, produced between 1955 and 1957.

only took it off to give it a clean and check it out, as bike would not rev after an 8 week lay up.
gasket kit from feked for the 376 went on fine, but have no idea whatsoever regarding jets etc. the needle is marked with a C, again google tells me that is a standard fitting.
with the bike being a bitsa and no history its a big learning curve.
do you think i should throw in a larger main jet anyway to see how it goes?
No air filter fitted, only an alloy trumpet which i cannot get off

Of course it depends how you ride it but a slightly too big main jet is safer for your engine than too small, you can adjust size later once run in a bit and you can do a plug chop (full tilt for a mile or so under load).

[V500]

the needle is marked with a C, again google tells me that is a standard fitting.

The C marked needle is usually the float needle for a copper float on a 276, but your bike has a Monobloc installed?

[rustyboots]

Hi Derek, thanks for the info, i'm getting more confused by the minute, google tells me this.
The Amal 376/58 is a 376 series Monobloc carburettor configured specifically for AJS 30 Twin and Matchless G11 Twin motorcycles, produced between 1955 and 1957.

only took it off to give it a clean and check it out, as bike would not rev after an 8 week lay up.
gasket kit from feked for the 376 went on fine, but have no idea whatsoever regarding jets etc. the needle is marked with a C, again google tells me that is a standard fitting.
with the bike being a bitsa and no history its a big learning curve.
do you think i should throw in a larger main jet anyway to see how it goes?
No air filter fitted, only an alloy trumpet which i cannot get off

Of course it depends how you ride it but a slightly too big main jet is safer for your engine than too small, you can adjust size later once run in a bit and you can do a plug chop (full tilt for a mile or so under load).

Hi Neil, riding is occasional and gentle tbh,
I dont understand what this means though. 
you can do a plug chop (full tilt for a mile or so under load).

[limeyrob]

A plug chop is a recognised way to check the mixture on the main jet.  You get the engine warmed up and find a decent quiet straight road.  You then ride at full throttle for a mile or so (more if possible) then cut the engine quickly, do not let it idle. Pull in the clutch and valve lifter and coast to a stop.  Then take the plug out and look at it. It should be light straw.
Of course its too hot to hold, its almost impossible cut the engine cleanly but its still a reasonable test.  I do still occasionally do plug chops because its a good way to separate the main jet from the needle.

[rhyatt]

Way back , 60 odd years ago , when AMAL and the British motorcycle industry were at their zenith, plug chops were part of the factory's development , alongside Amal.
They did these chops at the main jet end and then worked their way downwards , checking mixture strength against performance , needle position , then downwards to throttle slide then downwards to pilot.
In the knowledge that at full performance , the carburettor was correct

[rustyboots]

learning everyday

thanks guys

[Derek996]

Hi Derek, thanks for the info, i'm getting more confused by the minute, google tells me this.
The Amal 376/58 is a 376 series Monobloc carburettor configured specifically for AJS 30 Twin and Matchless G11 Twin motorcycles, produced between 1955 and 1957.

only took it off to give it a clean and check it out, as bike would not rev after an 8 week lay up.
gasket kit from feked for the 376 went on fine, but have no idea whatsoever regarding jets etc. the needle is marked with a C, again google tells me that is a standard fitting.
with the bike being a bitsa and no history its a big learning curve.
do you think i should throw in a larger main jet anyway to see how it goes?
No air filter fitted, only an alloy trumpet which i cannot get off

Carbs get swapped around. At some point in the bike's life a previous owner has fitted a carb from some other bike but it sounds like the jets haven't been changed to match the B31. Monoblocs are all pretty much the same except the jets get changed to suit different bikes. The /58 indicates what bikes it was jetted for when it left the factory.

[rustyboots]

Hi Derek, thanks for the info, i'm getting more confused by the minute, google tells me this.
The Amal 376/58 is a 376 series Monobloc carburettor configured specifically for AJS 30 Twin and Matchless G11 Twin motorcycles, produced between 1955 and 1957.

only took it off to give it a clean and check it out, as bike would not rev after an 8 week lay up.
gasket kit from feked for the 376 went on fine, but have no idea whatsoever regarding jets etc. the needle is marked with a C, again google tells me that is a standard fitting.
with the bike being a bitsa and no history its a big learning curve.
do you think i should throw in a larger main jet anyway to see how it goes?
No air filter fitted, only an alloy trumpet which i cannot get off

Carbs get swapped around. At some point in the bike's life a previous owner has fitted a carb from some other bike but it sounds like the jets haven't been changed to match the B31. Monoblocs are all pretty much the same except the jets get changed to suit different bikes. The /58 indicates what bikes it was jetted for when it left the factory.

cheers Derek, will try a larger jet or two