Weber Experts

[Snakebit]

What would cause the drivers side carbs to run rich and the passenger side to run normal? I thought I was close to dialing in my jet combination. I pulled the plugs on the passanger side and they were a nice tan color. When I pulled the plugs on the driver side they were black. So one side is running rich and the other side normal.

The carbs are all in sync. The fuel pressure regulator is at the first carb (rich side) set at 2.8 lbs at idle with a return line. Has any one ran different jets in different carbs or is the problem some where else?

[priobe]

Snake bit,

I would check the floats. If you are running an electric pump, I would fill the bowls and measure to see if 1 side is the same as the normal side.

I did this and used a seringe to extract the fuel. Place the fuel into a measuring cup and you will have your results.

I would also check the needle valve. I have seen different needle valves give different results.

[carmine]

While your at the floats check that they dont leak. In other words remove the float and shake to listen and feel if there is fuel that has leaked into them. If this is the case you will never be able to set and keep your float levels constant.

[Gaz64]

If you remove one emulsion tube from each carb, you then measure and compare the fuel level in the main wells to see if one side is higher than the other.

Floats should also be the same weight.

[priobe]

GAZ64,

I have heard this before in the past but does nto seem to work for me. Reason being, if you remove 1 etube stack and look down the well while removing the 2nd etube you will notice a huge difference in fuel height. For this reason I have decided to measure the bowl with both stacks in stalled remove the top cover then the float. Then take a seringe to suck out the fuel in to a container to measure the CC volume. This takes time but I know my float levels are exact. The seringe I use was about 8in long with a 1 inch diameter. I belive it was a 50 ML syringe

[ceslaw]

Could the length of the connection between the bell crank and the carbs be slightly different, left to right? This could result in exactly equal flow at idle when checked with the flow meter, but under throttle the flow may no longer be equal left to right causing one side to run richer than the other. Perhaps checking flow at higher RPM, say around 1500 RPM, near the top of the scale on the flow meter, will give you some indication. Since the problem involves both carbs on one side it suggests a linkage issue.

[Gaz64]

Originally Posted by Gaz64

If you remove one emulsion tube from each carb, you then measure and compare the fuel level in the main wells to see if one side is higher than the other.

Floats should also be the same weight.

Sorry if misleading, but I have said remove ONE tube from each carb.

Meaning remove the front tube from all carbs, it is only as a comparison test and is in no way indicative of the "true" fuel level since the level will drop with tube removal.

If after a test like this (which takes a fraction of the time compared to float level checking) there's a difference then you'll know which path to take.

The theory of equal throttle angle also has merit.

If half of the engine spends more average time at 25% and the other half at 20% and the engine is making "x" torque at that point, then the engine half at 25% is in a lower vacuum state (more load) than the 20% side.

The 20% side is "loafing along" for the ride, the 25% side is doing greater than 50% of the work.

The reverse could also be true if the idle circuit is too fat.

[Snakebit]

Thanks for the replys. I'll check the floats, but I think it is a linkage issue. It appears both carbs on the same side are in sync, but not in sync with the other side.