The Ford Barn

BILLF/TRF · 09-28-2010, 08:46 PM

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 · 09-28-2010, 10:53 PM

Try this link: Model A Carb Help

Chris in CT · 09-29-2010, 01:18 PM

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 · 09-29-2010, 05:37 PM

Sponsored Links (Register now to hide all advertisements)

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

09-28-2010, 08:46 PM	#1
BILLF/TRF Senior Member Join Date: May 2010 Location: Thief River Falls, MN Posts: 155	Running Rich 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?

09-28-2010, 10:53 PM	#2
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,899	Re: Running Rich Try this link: Model A Carb Help __________________ Mechanical engineering 101: If you put an adjustment knob, screw, bolt, or tolerance specs on something, some people will immediately fiddle with it. If you mark it DO NOT TOUCH everyone will mess with it.

09-29-2010, 01:18 PM	#3
Chris in CT Senior Member Join Date: May 2010 Location: Connecticut Posts: 272	Re: Running Rich 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!

09-29-2010, 05:37 PM	#4
Mitch Senior Member Join Date: May 2010 Location: Dayton, Ohio Posts: 182	Re: Running Rich Sponsored Links (Register now to hide all advertisements) Are you using an air filter? If so, try it for a while without one.

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