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#868712 01/11/22 12:56 am
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My 68 B44 has an AMAL 930-21. manual calls for a 930-11. Is there any difference? It has a 230 main, 107 needle jet, and I believe a 25 pilot jet. I ran a .023 guutar string all the way through the pilot jet. Ok. Here’s my problem. Runs lean. Have to keep the choke 3/4 closed to make it run ok. Needle is in lowest notch (richest setting), and pilot air screw only 3/4 turn out. Any ideas? Carb is not worn out. Boyer installed and strobed to proper timing.

Last edited by Roadwarrior; 01/11/22 1:01 am.

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Too much air coming in from somewhere. Bad or missing o-ring on pilot, idle adjuster or flange to manifold. Manifold leak. Flange bent,

Needle clip on bottom notch is richer, but this is for off idle at higher RPM.

Lowbrow Customs dot com has a decent video.

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Originally Posted by Roadwarrior
My 68 B44 has an Amal 930-21. Manual calls for a 930-11. Is there any difference? It has a 230 main, 107 needle jet, and I believe a 25 pilot jet. I ran a .023 guutar string all the way through the pilot jet. Ok. Here’s my problem. Runs lean. Have to keep the choke 3/4 closed to make it run ok. Needle is in lowest notch (richest setting), and pilot air screw only 3/4 turn out. Any ideas? Carb is not worn out. Boyer installed and strobed to proper timing.

Those are 2 stroke carb jetting. Do you have 2 stroke parts fitted to your carb? If not you’ll want to change the jets or fit a carb from say a 69/70. Which is what we did on my friends 68 B44. the only change we made at the time was took the slide from a 3.5 to a 3, I don’t believe it has been changed back.


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A 25 pilot is a 17 thou hole, if you have got a 23 thou string through there it will be oversized and running rich. So if you have the air screw out only 3/4 to get it to run you have some air leak.

Last edited by kommando; 01/12/22 5:35 pm. Reason: 19 should have been 17
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Check your needle, needle jet, slide, needle position, and idle circuit. Needle jets and needles wear but this will result in a richer mixture as they wear. Make sure you have a needle jet (.107) with two bleed holes in the flats. These are for four stoke motors. Make sure you needle has two grooves at the top. Three grooves is for 2 stroke motors. 4 grooves are for leaning out a motor. I have found that shop manual setups are general a bit rich. AMAL has a nice tech bulletin that is printed in Rupert Ratios book that does a good job of explaining all the changes that affect the mixture. The Haynes book setup calls foe a #3 slide and I believe I used a #3 1/2 slide. The 230 main should be OK. I used a 240 or 250 after porting the head on my B44SS. The needle jets come in .105, .106, .107 Try a stock setup with new needle jet and needle and go from there. I used to spend half a day changing things till I got it right. The end result is smooth acceleration through the entire range and a light tan plug after a long run. Also the idle circuit needs to be clean to aid in starting and low speed idle.

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Originally Posted by Mr Mike
The needle jets come in .105, .106, .107

And 0.1065.

http://amalcarb.co.uk/mk-i-Concentric-series/900-series/jets/needle-jet/4-stroke.html


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My 69 441 Victor Special has an AMAL 930-25 carburetor installed and it is the original carb. Not what the parts manual calls for.


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"Carb is not worn out" ........ wonder where that statement comes from? I know it might be possible, but lets face it the thing is likely to be upwards of 54 years old, they were made to a budget out of soft pot metal.
Air leaks are inevitable. You can spend a significant time, effort and frustration chasing them, changing needles, jets and settings, and still the bike will be difficult to start, and run rich one day and weak the next.

There is a reason they are still being made, and it isn't that modern bikes use them.

Tip .... when you eventually go ahead and buy a new one, get an extended idle screw as well.

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Got it figured out. Thanks all. O ring on pilot air screw was shot, and had a leak at the head junction. Seems to run pretty well now. Might get a new AMAL, but I’ve heard mixed reviews of them.


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Online resources indicate that carburetor ( fitted with its original insides )
was originally build/fitted as part of a pair of carburetors for some 1968 A65's
slides were #2.5 ot # 3 ... depending on the model .
with #20 pilots .


You have ...more than hogged out the pilot jet with the oversized guitar string .
.023 is approximately a number 45 pilot
With the flow rate approaching twice as much as specd .

glad its running better , but it makes me wonder .

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These AMAL carbs although quite basic, have a lot of adjustment capability. The have different needles, needle jets, main jet., needle position, slide size, pilot jet (on earlier carbs), pilot screw and throttle stop. When I got my first BSA back in the sixties, I did not know much about these carbs and my BSA 250 ,with an original carb setup ran rich. Later on, as learned about these carbs, I found it was pretty easy to get it tuned right...it just took some time and experimentation. Once I got it right, it remained reliable with only occasional cleaning of the pilot jet as preventive maintenance. Start with the manual setup, which is usually a bit rich, and go from there. You'll love when it is right...smooth idle, easy starts and smooth acceleration throughout the range.

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Originally Posted by Roadwarrior
Got it figured out. Thanks all. O ring on pilot air screw was shot, and had a leak at the head junction. Seems to run pretty well now. Might get a new Amal, but I’ve heard mixed reviews of them.

Having spent significant time cleaning, adjusting, and several sessions of " it can't possibly be xxxx " twice(!) I have bought 2 of the AMAL premiere carbs for my brace of B44s and had excellent, trouble free results with both.
As Mr Mike says, they are actually quite nice carbs, and once set up pretty stable ........ so long as they aren't 54 years old!

Of course having the right one fitted to your bike would also help. I got 930/38 s for both my '67 and the '69

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Dave,
Interestingly enough I picked up a Mik round slide and put it on my B44ss. After a jet change and some tweaks, I got it to run incredibly well from idle to WOT. It was so smooth, however, there was no adjustment for cold starts. It had an enricher circuit that simply did not work, and it would take many, many kicks to start it cold. I even tried spraying ether in the throat which made removal of the air filter necessary. Well, long story short, I will not have a bike that won't start easily so I went back to the AMAL and its crude tickler for those easy cold starts. I also remove the choke slides on AMAL's as unnecessary.
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Originally Posted by Mr Mike
Make sure you have a needle jet (.107) with two bleed holes in the flats. These are for four stoke motors.

Mr Mike


Back in 68 when this carb was jetted with the 107, 2 stroke and 4 stroke motors got the same jets, they only got revised in 69 and were later known as 2 stroke and 4 stroke jets. a 107 needle jet with 4 stroke (2 ring) needle will likely run too rich.

If you have a carb which is fitted with the 2 stroke style spray tube (slanted) etc (ie marked up correctly for a 68) then you will need to 2 stroke jets, if you have a 69-on carb (flat top spray tube) then jet it as a 69/70.

Not trying to pee on anyones chips here, but im simply stating because it may improve the bikes running by setting the carb as the manufacturer intended. The amount of times I hear "Amals are crap", when often they are just not jetted properly or worn to buggery.


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Allan,
I actually admire the AMAL. It was made to fit a very wide variety of bikes and with a wide range of adjustments to get the mixture right. My brother put a pair on his aircooled VW bug. I am a fan of the carbs because they work very well when you get it right. I think the bikes were probably factory jetted a bit rich to protect the engine from overheating. From a manufacturing viewpoint they are an engineers dream because of simplicity and one basic carb has many applications and interchangeable parts..

Mr Mike

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