miss during idle only? big twin

[pcrussell50]

almost no matter where i have the idle mixture needle set, it has an irregular misfire while idling that clears up and runs great under mid and high power.

it's not enough to keep me from using her, but i'd like to fix this. i don't think it's an air leak in the fuel system, because it runs grrreat under mid and high throttle. and it's a crisp miss like ignition. but i suppose a bad needle or seat for the idle mixture control is possible? what else? time for seafoam decarb?

wondering if it sounds to the gurus like the plug loading up under low load, then they fire better and clean up under higher loads? i run her at 25:1 because that's what i think the manual says to do, even though i think it has needle bearings, so it should be able to run 50:1? right? does running 25:1 tend to hasten the carbon buildup?

it's a 1959 super seahorse 35hp, rds21b

-peter

 

[tashasdaddy]

Re: miss during idle only? big twin

24:1 is correct mixture for that motor. you could have an air leak in needle packing.

http://forums.iboats.com/showthread.php?t=299680

 

[pcrussell50]

Re: miss during idle only? big twin

when you remove, inspect, and repack the needles, is it pretty much de-rigeur to rebuild the whole carb?

i'd hate to have to disassemble the whole carb to fix this unless a full rebuild is called for, since the only problem is the miss at idle.

-Peter