Idle too fast after carb rebuild

[ghoward]

I’m helping my friend get his new to him 1976 Pearson 30 with Atomic 4 sorted out. Initially it was showing symptoms suggesting a carb rebuild was necessary. I thoroughly cleaned and rebuilt for him with the Moyer kit.

Yesterday was our first trip out with the rebuilt carb. Much improved as expected but we found that it would only idle low (about 850) with choke on. Without choke it seemed to want to go right to 1500+. I have the idle mixture screw backed out 1.5 turns. We were in a little of a hurry so I didn’t get to try further adjusting the mixture screw in at least not systematically. But even backing out the idle speed screw to what must be all the way I couldn’t bring idle down without choke. I’m making a game plan for next steps when we can get back out to the boat and am wondering if this is more consistent with an air leak at the front as Moyer warns about for the 4-bolt model. If so I need to bring sealant and will probably want to proactively pull it and seal it before heating it up and making the job harder. Any thoughts?

[Al Schober]

Sounds like the throttle isn't closing. Could be the linkage or the adjusting screw on the carb.
The idle air screw is not the adjustment for idle speed. The screw for idle speed is back where the throttle shaft comes out of the engine.

[ghoward]

Ok, understood. I’ll try running with throttle linkage disconnected. I know the butterfly was closing during the rebuild so if it’s not closing now I’d suspect the throttle is holding it open.

Oh, and thank you!

[Al Schober]

Be careful. There's no spring holding the throttle toward the closed position. I suppose you could rig a spring or bungee to hold the lever on the carb towards the closed position. You don't want the throttle to inadvertently go wide open.

[ghoward]

Ah, thanks. I could hold it closed but good point that’s likely to go badly. I’ll start by checking that it’s adjusted to allow the throttle to close fully.