Running Rich

[BILLF/TRF]

I am not sure if this is normal for Model A's but my spark plugs are very sooty, black. I have tried adjusting the zenith carb (idle speed and idle air) but no change. I am wondering if my fuel mixture control, even though I have turned it clockwise against its seat, it may still be allowing some passage of fuel? Could it be that there is some pitting in this casting seat and that is preventing it from seating properly? Are there any vendors that put fittings in the casting for this seat?

 

[MikeK]

Try this link: Model A Carb Help

 

[Chris in CT]

Hi Bill, Offhand it sounds like one or both of your jets (main and cap) is drilled out too large. See if you can measure what the drill diameter is in both of these jets, and reduce them to printed specs or have them flow tested. The Zenith tends to run rich anyway, and needs to be minded so that it does not get out of hand. Happy Motoring!

 

[Mitch]

Are you using an air filter? If so, try it for a while without one.