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Ken and Paul,
On the Mikuni's for my Kawasaki 440 powered miniMax I am going to tap a line into the venturi of one carb. This line will run to a 'pulse chamber' to smooth out the intake pulses, then a tube will be run to each carb float bowl vent. The line from the carb venturi to the pulse chamber will be run thru the cockpit and will contain a needle valve to vary the signal to the float bowl. I know Ken knows this but others might not (or have never given much thought to what makes a carb work) - what we are doing here is diminishing the pressure difference between the venturi and the float bowl. When there is less pressure between the two the mixture will lean because less fuel will be sucked into the venturi of the carb. Close the valve completely and you have full pressure differential/vacuum and the mixture is at it's richest setting. As you open the valve you will lessen the difference in the pressure between the float bowl and the venturi thereby leaning the misture.
Ken Powell
Bryant, Arkansas
501-847-4721
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There is also a system used on snowmobiles that uses air bleed from the intake manifold that adjusts the mixture but I have not looked at it close vet but I have thought about playing with it.
There are two types, one is an after market kit called Dial-a-jet and the other is a factory setup that is automatically controlled by a computer.
I have never heard of anyone making anything for a Weber however.
Also I will note that a Weber differs from a crude aircraft carb or a Holly in that its very sensitive to air velocity and pressure, less air going through the Venturi will give you less gas so it compensates for alt to some degree compared to them crude carbs.
Ken
Hi, Ken thanks for the information. I did save a similar message that you previously sent describing how you used ram air to control the mixture on your Weber. If required, I could probably construct a similar system (If I pestered you with a few more questions). I was just hoping there was a simple solution, such as someone who came up with a mechanical lever type mixture modification for the Weber. I could easily weld or machine a slot in the mixture adjustment screw and attach a cable, but I suspect that the mixture screw would need to be turned in or out several turns, which a simple lever attached to the mixture screw would not accomplish. It might possibly turn the mixture screw 1/2 to 3/4 turn at max, which I suspect would not be sufficient enough to lean the carb enough for higher altitude. Thanks again for your input. I have also saved this posting just in case. sincerely, Paul Conner
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