[Peter 100]

Rick
Right we are now talking about the same nut 👍👍
Yes you are right the bottom one would not make any difference. If you have 19mm and mine is the 19mm think I will leave alone and play with the float as you say.
I actually got the bike fired up today the first time since I got it it actually ticked over nicely no smoke and the petrol stopped seeping out so its very near right I think.
I took a chance and bought it via an auction so never got the chance to hear it running a gamble I know but hey life's a gamble at the moment!!.
I am sure to be posting more questions as I go along.
Many thanks
Peter

[Rick Parkington]

Oh right, sorry Peter I didn't see the picture! The nut I was talking about is the one on the very bottom that covers the main jet. Certainly that one (aka 'Mixing Chamber Union Nut' in Amal-speak!) will alter float height.
Checking my 9A carb - a 29/001 M9A - this nut is 19mm top to bottom like yours. I also have a 10MDY AMAC stamped M90 (predecessor of the Type 29) also 19mm. 
Probably about to make another mistake here but I'm not sure I've ever seen optional sizes for a type 29, only the smaller type 6 (or 276). Certainly in the 1940 to 54 Amal settings list, there's only one 29 type but three type 6 - one of which (fitted to only a few models) is 3/16 longer - so there's your 5mm. Strangely I have been unable to  find any part number explanation for why this is fitted, if it's a  simple as to  clear a magneto or whatever it seems a bit of a drastic alteration although I'm sure 20s carb maker Charles Binks wrote that height makes little difference as long as it's not too high, so maybe it's that simple!
I think the fuel level s probably just that tiny bit too high and either your needle is worn/groove not quite right or maybe the float is too heavy - I guess you tried shaking it so see if there's any fuel inside? Also if it's copper and has been repaired it may have extra solder weight making it sit lower.
Cheers R 

[Peter 100]

Hello Rick
That's no problem it's good to get feedback.
I am a pretty new to this fuel level stuff so if I am wrong I hold my hands up.
But if you look at my sketch surely if you have a longer union nut it lowers the whole float bowl, the fuel level would be the same in the bowl in both cases but the level in the carb would be lower by 6mm.
In both sketches the carb is fixed to the engine but putting a longer union nut on lowers the float bowl.
What do you think.
Cheers
Peter

[Rick Parkington]

Hi Peter,  sorry I'm a bit low replying but the length difference is on the bottom of the nut not the threaded part and won't have an effect on the float level. As John and Steve have suggested the float needs to be lowered in relation to the carb body to adjust fuel level, either by lowering the float on the needle or by lowering the complete float chamber.
I know with the GP on a Gold Star, some recommend raising the float until petrol drips from the pilot screw hole and then slightly lowering it until it stops, suggesting that the air screw is supposed to be barely above fuel level.
As explained below, float height is supposed to be level with the top of the needle jet - but that means the actual 0.106" restriction, not the top of the brass 'spray' tube, so if you take a bit of solder (soft enough not to do  any damage) and fold or melt the end into a blob that won't pass through the restriction of the jet, so you can use it as a depth gauge. Take out the slide and drop the solder down into the jet, marking it off against the top of the mixing chamber, then you can check that against your plastic pipe.
I used it get very worked up about float height and how to check it was spot on but in reality it isn't all that precise, so just lower it until it stops overflowing and it'll be fine!
cheers Rick
   

[Peter 100]

Rick
Did a fuel level check with a bit of clear pipe and the fuel came to halfway up the diameter of the mixture screw.
With this in mind I think petrol is seeping out via the thread as it is wet underneath the screw.
so it looks like I need a longer union nut. Mine is 19mm and the long one is advertised as 24mm which I think would drop the level by 5mm and be below the screw. If the level is too low it just won't run I assume!! But it does seem worth a try as I don't like petrol dribbling out all the time!!.
Like Klaudius said it looks like I have had a replacement.
Cheers
Peter

[Rick Parkington]

Ha ha! yes Peter, the long nut is for the Type 29, I  think it just gives more clearance for the longer needle jet - you can use the short one I think - sure I had one on my 9A for years. It probably just means there's not much of a 'sump' if dirt gets in, making it more likely to get drawn into the main jet. I think I got my long nut from Martyn Bratby.
Cheers R 

[singleminded]

Quick fix is to rotate the card a little anti clockwise on the stub, it lowers the float bowl a bit and so the carb fuel level drops.
John

[Peter 100]

Just one more question chaps.
Klaudius just posted a picture of the different length union nuts see post below.
Most of the reference pictures I have seen the carbs have the longer type. Mine is the shorter one.
Steve and Rick do you two have short nuts! (excuse the pun)  or longer ones on your bikes?
Peter

[Peter 100]

Klaudius
Thanks any information is good.
I didn't realise they made different sizes for the end cap/nut very useful.
That's a device for measuring petrol level I assume.
Peter

[klaudius]

Sorry for bringing myself in again. I saw that your chamber was not intended for the carburetor. Parts of different heights could also have been installed over the course of time. The cheap device can be used to simulate the state several times and, above all, to close the needle.
Klaudius

[klaudius]

If the float is correct, the needle / chamber cone seal could also be incorrectly shaped or just a little worn. I usually help myself with a small, slow-running cordless drill (I have children and tinkering time is precious) and some toothpaste. This allows you to fit the cone of the needle to the cone of the chamber. I prefer old English original parts than today's replicas.
I wish you much success.
Klaudius

[Peter 100]

Cheers Rick
Great clear explanation I will be an expert soon 😁
Well maybe not.
But some good info.
Ta Peter

[Rick Parkington]

Hi Peter,
Just to throw in my six pennorth... The similar carbs that don't have the 4 holes are later - post-war - ones. The holes are not overflows - although they do act as such - they are the primary air supply. Carbs obviously work on the venturi principle: throttle-supplied air blowing over the needle jet draws fuel up into the airstream where it atomises into sort of aerosol droplets. But it isn't neat petrol that is drawn up, there's a primary air system that partially atomises the fuel in advance, and these 4 holes supply the air for that. Later carbs, without these holes, instead have a diagonal hole drilled down inside the 'bellmouth' side of the carb that marries up with a hole in the jet block. The reason for this was allegedly that the Ministry of Defence, who wanted air filtration (fair enough - they were headed for North Africa...) were not happy that this primary air bypassed the filter. Nortons (alone, I think) were different again, having no holes but a flat milled off the back of the jet block to let the air in.
The problem with all this is that it means there are three types of jet block to get muddled with as well as different sizes and left/right options!
As others have said, it shouldn't leak just by turning the fuel on, upright but if you tickle the carb it will drip and I find they do sometimes if you  start the engine and stop it again quickly.
You soon get used to people coming up saying 'Here mate, you're bikes dripping petrol!' and smoothly telling them 'Don't worry, it'll stop in a minute...' !
Cheers R

[Peter 100]

Cheers Steve
It's just when you're new to these sort of things I panic a bit!! 😁
But that's good to know.
Peter

[Greybeard]

Stop worrying about it, Peter. Its normal. If petrol comes out of the holes its already flooded enough for starting. You dont need the float bowl to be brimming. 

Steve

[Peter 100]

With regards to the fuel coming out of the holes in the carb which are shown in the picture attached. I have noticed similar carbs for sale on ebay and other sites but there are no holes is mine unusual or did they stop putting them in at a later design.
Also with the level of the fuel being close to the holes when I use the tickler fuel comes out of the holes in the carb instead of the tickler itself again is this usual.
Any thoughts.
Peter.

[Peter 100]

Klaudius
OK thanks
Will check it out.
Peter

[klaudius]

Red is the fuel level.
Green is leaking.
With unscrewing you can comfortably adjust the stand very precisely in the cellar with a glass of wine. I tried a gasoline tank that you can get for little money on Ebay.
One more thing. There are new chamber swabs for sale in various qualities. The ones from India are a little longer and cause overcrowding ...
Best regards
Klaudius

[Peter 100]

Thanks Klaudius
Is the red line the petrol level and the green the overflow?
Peter

[klaudius]

Hi
When the chamber with the lower screw connection is off, the inlet should be stopped by the float about 2 mm before the overflow (screw carburetor).
greeting
Klaudius

[Peter 100]

Thanks Steve
Will have a look into that.
Peter

[Greybeard]

The level should be just a tad below the top of the jet so pretty close to those drains. One of the best explanations Ive seen of various early carbs is in a book called ' Motorcycles in a Nutshell'.
https://www.amazon.co.uk/Motorcycles-Nutshell-1923-Explanation-Motorcycle/dp/1908890185

Steve

[Peter 100]

Steve
Thanks for your comments.
l have put an extra fibre washer between the bowl banjo and carb like you did plus bent the brass clip on the float a smidge and it has stopped the overflow. I did a level test using a clear bit of tube and the level is pretty near those drain holes. It does seem a bit high but not coming out.
I wonder what the actual level should be?
Cheers
Perer

[Greybeard]

Hello, Peter.
For what its worth, Ive had a similar irritation on two machine. One is a 1926 AJS G8 which dripped petrol from the carb whenever I used the prop stand. Evenually the penny dropped The float bowl being on the right hand side was effectively raised above the level of the jet when the bike was leaning to the left. The easy way to solve it was to use the rear stand and turn the fuel off.
The other bike is a 1949 Matchless G80S that persistently ran a tad rich. I cured both by fitting a thicker fibre washer on top of the float bowl banjo which effectively lowered the float bowl just enough to sort it. Naturally, I'd been though all the other checks and re-cut the taper at the bottom of the float needle before lapping it in with jewellers rouge and chrome cleaner before hitting on the solution.
My 500 Lion that suffered similar bouts of more pronounced incontinence, especially when warm, was sorted simply by removing the grooves worn into the float needle before lapping it in.

Steve

[Peter 100]

Hello to all.
As some will know I am fettling a newly acquired bike and have had some great info about the carb it is a 29/001 type however,
With the carb still on the bike I removed the float bowl and jets cleaned them all and checked and tested the float which works and cuts off the supply of petrol when full.
upon re assembly and filling with petrol via the tank petrol starts to run out of the carb via the two holes in the picture attached. I assume these are overflow holes but why the leak.?
Is the float too high?  I only have one notch on the float needle so cannot really alter the level.
Any suggestions please.
Cheers
Peter