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Recently I performed a new modification to my brand new Amal 930. I'm not sure if anyone else has attemped something like this before, as I couldn't find any info on it. Anyway.....

I've always had problems with the new amals (or most of the old) that did not have the interchangable pilot jet, mostly running too lean without any more adjustment. So, I thought, why not make an orifice on the gas side of the pilot circuit and use a needle to adjust the amount of fuel, just like the air screw? So I performed this by drilling out the hole opposite of the airscrew and driving out the pilot bush. Next I drilled just passed the passage perpendicular to the bit. The amal needles are 10-32 thread, so I tapped and inserted the needle, tightening to make a seat in the orifice. Just yesterday I ran the bike and it is unbelievable how well it worked. Finally the mixture is correct and the throttle response is lightening fast.

I'll post a diagram and possibly a video of the engine running in the next couple of days. I just wanted to get a start letting my fellow british bikers know about it.
 

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Interesting.

Let me see if I follow what is being suggested. I think I got the part about taking out the slug that secures the pilot jet. The pilot jet itself is then removed which in turn is then replaced with an extra air screw to allow an adjustable metering of the fuel?

A few more details would be really nice and better yet a diagram or two? Sounds like it gives you much more control but on the other hand you really could have a headache if the adjustments go out.
 

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Hi
I was wondering if you have any updates on this modification? :)
I have been thinking of idea myself, so therefore it could be interesting to know how it has turned out after using it for a longer time period.

-kind regards
 

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I was wondering if you have any updates on this modification?
I have been thinking of idea myself, so therefore it could be interesting to know how it has turned out after using it for a longer time period.
11 year-old thread, so not too likely to get replies. However, he reported immediate findings of significant improvement, and I don't see how it could deteriorate...
 

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11 year-old thread, so not too likely to get replies. However, he reported immediate findings of significant improvement, and I don't see how it could deteriorate...
I can, if it's an 11 year old Mk1 concentric that has actually been used. Add to that that new Mk1's now have a removable pilot jet!
 

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11 year-old thread, so not too likely to get replies. However, he reported immediate findings of significant improvement, and I don't see how it could deteriorate...
I know its an old thread.
But if you look on his profile, he actually have been online earlier in 2020
 

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I can, if it's an 11 year old Mk1 concentric that has actually been used. Add to that that new Mk1's now have a removable pilot jet!
I know the new ones got a removable pilot jet.

But the special thing about his carb modification is that he didn't use a removable pilot jet after drilling the push-in one out.
He used an air-screw instead, which might end up giving false air problems (don't know if it's called this in English), in the carb.
 

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Recently I performed a new modification to my brand new Amal 930. I'm not sure if anyone else has attemped something like this before, as I couldn't find any info on it. Anyway.....

I've always had problems with the new amals (or most of the old) that did not have the interchangable pilot jet, mostly running too lean without any more adjustment. So, I thought, why not make an orifice on the gas side of the pilot circuit and use a needle to adjust the amount of fuel, just like the air screw? So I performed this by drilling out the hole opposite of the airscrew and driving out the pilot bush. Next I drilled just passed the passage perpendicular to the bit. The amal needles are 10-32 thread, so I tapped and inserted the needle, tightening to make a seat in the orifice. Just yesterday I ran the bike and it is unbelievable how well it worked. Finally the mixture is correct and the throttle response is lightening fast.

I'll post a diagram and possibly a video of the engine running in the next couple of days. I just wanted to get a start letting my fellow british bikers know about it.
 

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I know the new ones got a removable pilot jet.

But the special thing about his carb modification is that he didn't use a removable pilot jet after drilling the push-in one out.
He used an air-screw instead, which might end up giving false air problems (don't know if it's called this in English), in the carb.
I'm sure that the modification can be made to work with some tuning, but most old concentrics are worn out by now, the new AMAL/Burlen ones are so much better made. A comment I would make (and you'll get this from others as well) is that modern fuel often needs to be slightly richer than the old setting, I often find I need to go 1/2 a size less on the slide, for example, to stop hesitance from idle. What problem are you trying to fix?
 

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I'm sure that the modification can be made to work with some tuning, but most old concentrics are worn out by now, the new AMAL/Burlen ones are so much better made. A comment I would make (and you'll get this from others as well) is that modern fuel often needs to be slightly richer than the old setting, I often find I need to go 1/2 a size less on the slide, for example, to stop hesitance from idle. What problem are you trying to fix?
I'm actually not trying to fix a problem right now. :)
But I'm building a 500cc triumph frisco chopper. And are looking for small modifications to make the engine perform a little better. I know there's a lot of other things to do, and I have done a lot of them already, like better conrods, head with bigger intake-valves, morgo oil pump, 9:1 high compression pistons etc.
I just got a general interest in customizing and modifying parts, to make them better.
I would rather have a tuned single amal carb than dual carbs like the daytona. And I don't find many threads about upgrading/tuning an amal carb, only about getting them back to stock performance.
So if you know any other tricks, I will be grateful.
 

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I'm actually not trying to fix a problem right now. :)
But I'm building a 500cc triumph frisco chopper. And are looking for small modifications to make the engine perform a little better. I know there's a lot of other things to do, and I have done a lot of them already, like better conrods, head with bigger intake-valves, morgo oil pump, 9:1 high compression pistons etc.
I just got a general interest in customizing and modifying parts, to make them better.
I would rather have a tuned single amal carb than dual carbs like the daytona. And I don't find many threads about upgrading/tuning an amal carb, only about getting them back to stock performance.
So if you know any other tricks, I will be grateful.
But as i know, the pilot jet should only affect idle and 1/4 turn on the throttle. So i don't understand how it improves the throttle response overall? This should only be up to 1/4 turn on the throttle, as the other components in the carb take over the air and fuel flow/mixture after the 1/4 turn.
 

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Hi, I can tell this, on Premier concentric with removable/changeable pilot jet. When you stray far from 1.5 turns out on mixture screw (which is an air screw) it changes/disrupts the velocity of the air in idle circuit. Carb never works quite right.
I’ll likely be dealing with this yet again. Today checked mixture screws. Both at 3/4 out. Has .017 (2 ring jets).

Ill keep you posted on tuning

Back to to the carb mod I suppose he turned pilot jet into a fuel mixture screw. Then could set normal mixture air screw to 1.5 turns & fine tune mixture with fuel screw. Depending on tolerance of pilot jet, adjustable could make good improvement.
This is basically what the changeable Pilot jet in premier accomplishes.

1/4 throttle?? Mark your grip & go for a nice long ride. How often do you cruise above 1/4 throttle?

How often 1/16-1/8? Pilot jet can make a big difference especially if cutaway is on lean side.
Don
 

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Hi, I can tell this, on Premier concentric with removable/changeable pilot jet. When you stray far from 1.5 turns out on mixture screw (which is an air screw) it changes/disrupts the velocity of the air in idle circuit. Carb never works quite right.
I’ll likely be dealing with this yet again. Today checked mixture screws. Both at 3/4 out. Has .017 (2 ring jets).

Ill keep you posted on tuning

Back to to the carb mod I suppose he turned pilot jet into a fuel mixture screw. Then could set normal mixture air screw to 1.5 turns & fine tune mixture with fuel screw. Depending on tolerance of pilot jet, adjustable could make good improvement.
This is basically what the changeable Pilot jet in premier accomplishes.

1/4 throttle?? Mark your grip & go for a nice long ride. How often do you cruise above 1/4 throttle?

How often 1/16-1/8? Pilot jet can make a big difference especially if cutaway is on lean side.
Don
thanks for the reply.
And you're right, you will never use that much throttle when cruising, and quicker response on the throttle will be a great upgrade. :)
 

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Richard Darby in England [look him up on TOL] does this mod. I have had it done to my Trident carbies.

or you could drop me a PM and I'll send you his email if interested.
 
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