Thread: 4 Barrel Carb Linkage Modification

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What you're missing is how levers work.

Pulling a longer lever the same distance as a shorter lever results in less angular rotation.

In this example, the point where the lines come together at the bottom is the throttle shaft. The pull is 1" for both levers. The 4" lever would rotate about half as far as the 2" lever. That means you would have to pull the throttle cable further, resulting in more pedal movement.

Experiment with different lengths of levers, and you can tune your pedal travel.

Carb.jpg

Originally Posted by Henry Rifle

What you're missing is how levers work.

Pulling a longer lever the same distance as a shorter lever results in less angular rotation.

In this example, the point where the lines come together at the bottom is the throttle shaft. The pull is 1" for both levers. The 4" lever would rotate about half as far as the 2" lever. That means you would have to pull the throttle cable further, resulting in more pedal movement.

Experiment with different lengths of levers, and you can tune your pedal travel.

Attachment 62935

And to further clarify Jack's excellent post, from idle to wide-open-throttle (WOT) is right at exactly 90 degrees of rotation, from butterfly flat level to straight up. Your picture doesn't show it, but if the sheath of the throttle cable is not constrained at both ends that adds to your problem.

The ideal configuration of your throttle lever on the carb would be angled 45 degrees towards the front of the engine. WOT would then be about 45 degrees to the rear. That gives an even pull throughout the throttle range.

Carb.jpg

Triker---we need a photo showing more of your linkage and cable mounting-----------and please include the foot pedal area

With the pedal floored is the cable pulled into the sheath, no braided wire showing?

Could the sheath just need to be trimmed back to allow the cable more travel ?

How much are the butterflies opening, how much more travel is needed to obtain WOT ?

most likely the problem is on the pedal end and we are trying to crutch him thru a carb end fix .. the carb worked fine in stock configuration .

Originally Posted by HOSS429

most likely the problem is on the pedal end and we are trying to crutch him thru a carb end fix .. the carb worked fine in stock configuration .

I agree, and was thinking the same thing when I saw the thread pop up in "Today's Posts". Gotta be on the pedal end, plus maybe some basic cable/mount issues.

I feel a little silly now. All those trees getting in the way of my view of the forest.

Originally Posted by Henry Rifle

I feel a little silly now. All those trees getting in the way of my view of the forest.

Jack, I think that everything you posted was of value, in order for Triker to understand the length of throw issues. That said, I've never seen a problem with the OEM bell crank relative to pedal travel, but he's the one who posted the question.....