carb air leak?, occasioally surging idle Options

[VaccaRabite]

I am having a weird issue with my carbs.

They will go along fine at 1100 RPM idle all day. Suddenly I will stop at a sign or red light and the idle will climb from 1100 to 1700 and my car will start making unsynced carb noises. Sometimes it will settle back town if I tap the gas peddle, sometimes not. Once the idle surges, it will be like that for a while when I stop, and then it will suddenly drop back down to 1100 RPM and and behave nicely.

I am guessing that I have an intermittant air leak in one of my carbs. Anything else I need to be looking at?

My theories, in order of what I think is likely:
1) air leak somewhere
2) gas leaking past the inlet valve
3) weirdness with the linkage

I have not been able to recreate the issue at home, its always when I am on the road so I don't yet know which carb is acting up. Its worse if I am driving the car hard, but will happen when I am just cruising around town some too.

Ideas?

Zach

[904svo]

I don't think you have a air leak, air leak would made the engine slow down. I would suggest you check your linkage it sound like its twisting and hitting something
at times. I had a problem like this one time and found the spark plug wire was getting caught in the linkage and stopping it from hitting the idle stop.

[VaccaRabite]

I'll take another look at the linkage. If it is the linkage, it will be just another reason why I want to get rid of it. Man, I do not like the cross bar type of linkage.

Zach

[Cevan]

Zach, your next winter project should be to make a cable linkage (or buy one if one comes to market). Mine's been working great for almost 2000 miles.

[rhcb914]

I also vote to look at the linkage. Make sure both carbs fall back to idle at the same time and one doesn't lead the other. I've had all sorts of weird idle issues that traced back to linkage.

The other thing that I have noticed is that many of us adjust the linkage when the car is only somewhat warm or cold. The engine expands quite a bit and that can exacerbate a minor bind when cold creating a major one when hot. Well maybe not major but you get the picture.

Go beat the crap out of the car get it really hot then bring it home adjust the linkage. Make sure there is no preload on either carb.

Keep at it! It's just a machine you can beat it (IMG:style_emoticons/default/smile.gif)

[VaccaRabite]

Zach, your next winter project should be to make a cable linkage (or buy one if one comes to market). Mine's been working great for almost 2000 miles.

I so intend to buy one as soon as they come on to the market. I hate my hex linkage. With a passion.

Zach

[bobhasissues]

I had similar issues and found that if the "arms" that connect your throttle shafts to your drop links have any rotational play in them then you'll never get the carbs right. To check, disconnect the drop links and hold your idle speed adjusting screw against the stop and try to move your carb arms. If they have free play you will never get the carbs to synch up right. Good luck.