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Looking for some stock carb help.


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I picked up a 76 620 a few months ago. I was having problems with it dying or having a rough idle when I came to a stop. I decided to rebuild the carb while I had it in the garage redoing the brakes. Now it might die or get a idle at 1000rpm-2500rpm different everytime. I was going to try and adjust it but not sure where to start since it's all over the place. I did loose a spring out of it held down a ball bearing replaced it with the spring from a ink pen. I can't be sure but it seemed to have enough force to act the same plus it was the only thing I could fit in the hole. I guess next time I won't work next to a gravel driveway.

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Hmm that link opens a page that doesn't have a Hitachi link on it.


Now it might die or get a idle at 1000rpm-2500rpm different everytime
Sounds like something is loose: carb gasket, or jets or air bleeds or something. Missing or cracked vacuum hose maybe.
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It's a one way valve similar to the one under the accelerator pump to prevent sucking air back from the accelerator pump discharge nozzle. Wouldn't cause your idling problems.


Throttle cable may be too tight or throttle shaft worn and throttle plate sticking in the bore. Push the throttle closed by hand. If poor idle turn the idle speed up slightly then turn the idle mixture screw in untill the idle quality drops. Turn the screw out till it improves and revs up. re adjust the idle speed down to about 600-700 RPMs and try adjusting the mixture screw again to get the best smooth idle speed, re adjust the idle speed down and keep alternating back and forth until the mixture is right and the idle speed is adound 700 and smooth. Between the screw in too far or out too far may be 1/2 to 3/4 of a screw turn so just guess where half way between is and set there.

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Thanks that helped I see now what the problem is. When I put the carb on I had the fast idle adjustment like it showed in the diagram on the rebuild kit and how it was before cleaning on the first notch of the cam. Every time I rev up it stops at a different notch or doesn't even make it to the notches. I checked the throttle it seems free and returns and the cable has a slight amount of slack. The spring has tension sometimes it works sometimes it doesn't. One the first notch adjusting the mixture it idles 2000-2500rpm if it stops before it even makes contact with a notch I can get a decent idle at 1000rpm. I try any lower and it gets rough.

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