Carb Idle debug

[chuckmoon]

I have two boats ('82 & '84 Bayliner Capri). Both have a 4 cyl Volvo AQ125A engines and Solex downdraft carbs. Over the winter I overhauled both carbs. One carb works perfect. The other will start if the idle is very high...as I decrease the idle speed below 1200 rpm, will not maintain idle speed without dying (the other carb idles smoothly at 800 rpm). If I swap the lower half of the carb (that holds the butterfly value) the problem moves. I have been told by friends that I must have an air leak past the valve. Any recommendations how I can find where the leak is?

 

[chuckmoon]

Re: Carb Idle debug

I inspected for flatness but assumed that the gasket would provide an adequate seal. I will do a closer inspection since all fingers seem to point to this area. Sometold me to apply air pressure and look for air leaks with soap film. Have you ever tried this technique?

 

[Coors]

Re: Carb Idle debug

Did you soak then over-night with real carb cleaner? And blow all passages out with a compressor? That is the only way to rebuild a carb.

 

[chuckmoon]

Re: Carb Idle debug

Yes, I used real carb cleaner 2 nights and blew out with air.

 

[Kessi]

Re: Carb Idle debug

With engine running, spray carb clean around the base of the carb. It will stumble when you hit the leak.
Chances are the bushing for the control arm to the butterfly valve is worn. It would probably wiggle back and forth to indicate the wear.