ET: Engine (Twin) 32mm Amal premier Concentrics

favouritepants

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Hi all imrunning 32 mm Amal Concentrics with removable pilot jet wit a no3 slide 106 needle jet needle in middle position 230 main jet and a17 pilot jet and my bikes idles well but bogs down on take of before launching away so I’m thinking bigger pilot jet your thoughts and or recommendations someone must be running these and I know every engine is different it any help would be great
Cheers
 

Normski

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If your idle mixture screws can be adjusted to give a good idle and are within the range of say 1- 2 turns out (but better 1.1/4 - 1.3/4) then your pilot jets are ok. A 107 needle jet would be richer a 3.1/2 slide leaner?
 

Bill Thomas

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I would try a 3.1/2 slide, Not sure what your petrol is like, But I have had to weaken my Bikes, With the Rubbish we have. Cheers Bill.
 

van drenth

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Be aware that there are different tapers on the pilot screws, and also the O rings which comes nowadays in the repair/overhaul kits are too small and after fitting those the pilot screw leaks air and will turn out by themselves.
Regards
JC van Drenth
 
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favouritepants

Forum User
VOC Member
Be aware that there are different tapers on the pilot screws, and also the O rings which comes nowadays in the repair/overhaul kits are too small and after fitting those the pilot screw leaks air and will turn out by themselves.
Regards
JC van Drenth
These premiers are brand new but I will remember that whe it comes time to overhaul
 

favouritepants

Forum User
VOC Member
If your idle mixture screws can be adjusted to give a good idle and are within the range of say 1- 2 turns out (but better 1.1/4 - 1.3/4) then your pilot jets are ok. A 107 needle jet would be richer a 3.1/2 slide leaner?
The front cylinder is at about 1 turn out and the rear is 1.5 out I’m thinking it needs more fuel or though it seems to be spitting back more on from cylinder then rear. I should mention I have not widened th manifold at all which could be a issue considering it’s going from 28mm manifold to 32mm on carby
 

Bill Thomas

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VOC Member
Sorry , If it's spitting back, It's weak, So forget what I said about 3 1/2 slide.
Maybe an air leak, Maybe too far retarded on the ignition, Was it OK before you fitted new Carb's ?.
Don't worry about the change in shape on the manifold.
Are the carb's sitting straight and level ish ?.
The other thing is float height ?.
Is this a tuned Engine, Or standard ?.
Cheers Bill.
 
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