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The Saga continues 40DCOE weber


Jedi Trainee
Ok Morris sent me a colortune, I have followed the instructions and warmed the engine up so with the choke off it is idling around 750rpms. I shut her down and installed the colortune in all 4 spark plug positions. YELLOW is what I am getting. Through 4000 rpm. I cranked the idler needles down which helped some, a little blue. But when I rev her a little more aggesively she stumbles and bogs still. When this happens the colottune goes black, no fire. And when I let up she catches and it is brilliant YELLOW.

What I did have:

30 = choke size
4.5 = auxiliary
125 = main jet
170 = air corrector jet
F16 = emulsion tubes
50/F9 = idle jet
40 = Pump jet
Plugged = accelerator pump discharge

What I have now:

30mm = Choke
4.5 = Aux Vent
120 = Main Jet
190 = Air correction Jet
F16 = Emulsion Tube
40F8 = Idler Jet
35 = Pump Jet
Plugged = accelerator pump discharge

I tried the 155 air correction jets but it ran worse, when I got to 190s she ran about the best. There has got to be somthing else going on. I have rebuilt her and installed new gaskets all the way around and installed new lead washers under the pump jets. It just seems I am missing somthing.
One thing I noticed was when I accelerated using the spring return lever she advances more smoothly, when I use the thottle lever it is not as smooth, stmbles a little.
Any other Ideas, the bank want my first born.
My pnone number is 334-797-3469 if you want to hear what she is doing. After five is best CST.


Don't have any advice, but I feel your pain.

Stay strong.


Great Pumpkin
Country flag
A pair of SUs and make it sing.

Sorry I just had to say it.


Jedi Knight
Why did you plug the accelerator pump discharge? Sounds like you are going lean on rapid acceleration. Weber's are not constant depression carburetors.


Jedi Warrior
What I have now:

30mm = Choke ok
4.5 = Aux Vent ok
120 = Main Jet 135
190 = Air correction Jet 180
F16 = Emulsion Tube F2
40F8 = Idler Jet 45F9
35 = Pump Jet 50
Plugged = accelerator pump discharge ok

assuming you are using a centrifugal advance only dist ?

the curve has a LOT to do with part throttle application.


Jedi Trainee
Fule pump is new 2.5 psi, New needle valve for float. Float is 8.5mm rest to 15mm extended. Have not change distributor, nor messed with it except to verify timming.


Jedi Trainee
That is what the weber tech told me to do, 1275cc engines are suppose to have plugged discharge pumps, as the fuel bleeds back into the bowl with out getting the correct stream from the prump jets. Was only getting a 3-4' steam when the thottle was engaged, now I get 6-8' stream.


Jedi Trainee
It is a vacum advanced distributor, have considered going electronic. Still need to pick up a can of carb cleaner and spray it around the intake manifold to rule out an air leak. Was told the engine will increase in speed if it is sucking air from anywhere but the venturis. One more thing to check. While I am at it I will pick up a new distributor cap, points and rotor.

The weber tech told me that the F2's are for top end and dont do well on the bottom, whereas the F16's are for the bottom end.

Pretty much any help I will take and try just about anything except switching to SU's which I dont have "Jack" hehehe Just trying to get what I have going.

Will call weber and see what evaluation and cleanup would cost. If it works good in their arena then I can stat looking at the engine more closly.

What intake manifold are you using? I have a cannon 308 on mine.
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