What's the theory behind carb linkage adj.?

[EricB]

Hi all,

I've always wanted to ask but never got around to it...

What is the theory behind carb linkage adjustment?

By that I mean to ask: on a set of triples (doesn't matter size or brand), you've got the main throttle shaft that runs the length of your manifold to which are attached three arms (on my mikuni manifold these are cast & fitted with three different threaded positions) to which are attached three adjustable length rods that connect up to each carb...

Ok so... adjusting them so that they are all at the same length and thus the carbs open at the same time and the same amount is one thing - fine no problem there....

What I'm wondering about is for example the three cast arms I mention above attached to the main throttle shaft on my mikuni manifold, well they have three threaded holes I can use... which one should I use & why? Depending on which one I end up using I then have to either lengthen or shorten the corresponding adjustable length rods...

Do you all see what I'm asking about?

Maybe a sketch is needed here...

Lemme see...

I looked through the gallery and grabbed a pic of someone's triple mikunis... what I am calling the "cast arm" above I labelled A in the picture, what I am calling the "adjustable length rods" I labelled B in the picture...

So what's the advantage of shortening the one and lengthening the other or vice versa... I am guessing it affects how much travel you get at the gas pedal but can't figure out which combination gives what result....

Thanks all,

-e

[kmack]

Here's my guess:

Keep in mind this is subject to misinterpretation and my inability to put forth in words exactly what my brain thinks...:stupid:

It looks like the adjust is there for one of two reasons (or both).

1) My first thought would be that placing the carb linkage in the farthest hole on the arm away from the manifold would give a slower throttle response. That in turn, would make it easier to make minor adjustments to throttle position using the gas pedal while driving. Basically, better throttle control.

Putting the carb linkage in the hole in the arm closest to the manifold would give you quicker throttle response due to having a shorter distance to travel while opening the throttle butter-flys. Kind of a course vs. fine adjustment type of control.

2) My other thought would be to maybe help overcome some of the same type syptoms in the bell-crank set-up as with the stock Z throttle linkage issues at the firewall. But I think my 1st opinion above is a better reason.

So tell me, did any of this make any sense at all? I know in my mind it did....

[sblake01]

Makes perfect sense to me, kmack. I don't have any personal experience with Mikunis on Zs but I do have a single Weber 40DCOE on my L320. The first adjustment you describe makes it easier to drive normally while the second one is kind of like a quarter turn throttle on a motorcycle.

[EricB]

Ok gotcha...

That makes sense... I just needed someone who knew to put in down on paper...

Thanks,

-e