After reading the weber adjust page really opened my eye's on how much goes into tuning these carbs. I realized that my mixture screws are 2 1/2 turns out way to much so according to weber my idle jet is to lean.

I would be looking at two areas that will influence part throttle [cruising] stumble /popping conditions. 1, as already suggested above is the incorrect choice of idle jet. As already stated the idle jets meter fuel for the idle and progression ccts, which by the way is 80 -90 % of most of your driving. WOT is rarely used in the scheme of things. 2. poor carb balance between carbs will also produce similar symptoms. A carb balancer /synchroniser will be your best friend to sort that out.

> These are new carbs I never touched them yet.

Have you set the idle and mixture screws for best lean idle? If not it won't run correctly. Weber explains how to set best lean idle here.


> I bought 28mm chokes ... I think I need to use a 165-180 air corrector jets and Main jets 110-130.

That's a HUGE range. Start with 28*4 = 112 main jet and 168 air corrector.

there is plenty of good info out there but the main thing is to only work on one area at a time.
If you can get access to a wide selection of jets for tuning it will make it a lot easier and quicker (especially if you only need to pay for those you eventually "keep").
If you can find someone that knows these carbs and has a dyno, you will get it nutted pretty quickly but at $$, doing it yourself will take longer (but is satisfying and cheaper (maybe, if you don't blow anything up and don't have to buy heaps of jets !)).

Hope you can sort it out and good luck!

For the low-speed circuit, follow Weber's easy advice: http://www.redlineweber.com/html/Tech ... ment_layout_typical_i.htm

what is your setup?

single 40DCOE or twin 40DCOE?
A12 or ??
Modified?

Air correctors - too lean (large hole) causes a miss at near max RPM, too rich (small hole) it will be soft and not give full power
Main jets - affect max RPM similar to air correctors
Emulsion tubes - affect the acceleration phase from progression onto full throttle and the main circuit coming into operation
Idle jets - affect alot! idle, off idle and progression onto the main circuit are all determined by this!
Aux venturi - also important for response
Choke - as mentioned sets the effective rev range of the engine
Accel jet - purely there to fill the hole created with sudden opening of the throttle causing a lean spot, you should be able to drive without these if the throttle is opened gently enough, don't use them to hide a weak progression!

I thought cruise was anywhere from 20% open on ... but now I stand corrected.

FULL THROTTLE is combination of mains and power valve.

At cruise you are primarily using the idle and progression circuits. The main jets and air correctors only really come into play once the throttles are 70-80% open.

Idle and progression are what give you driveability so you need to sort out your low rev issues.

What idle jets and holders do you have installed?
How many progression holes are there?

By all means work on the full throttle jetting but do it after you have fixed part throttle response!

Main jet is 115mm and Air corrector is 200mm .
These are new carbs I never touched them yet.
And I forgot to mention I bought 28mm chokes.Haven't got them yet.
I think I need to use a 165-180 air corrector jets and Main jets 110-130.

But if you are using the stock size jets for 30mm chokes it should be OK. Steady cruise air/fuel ratio is good from 14.7 to 12:1 and will not cause popping -- for nearly all engines except those with high overlap camshafts.

More likely is caused by a vacuum leak... unless someone changed the jets previously.