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Hi idle [2400RPM] CO adjustment

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skinsgamer

skinsgamer

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Hi again, I'm still playing the California smog challenge. We've now got my 78 midget with original ZS carb passing HC and CO at idle. However, when we do the 2400RPM check HC stays in limits, but CO goes way up.

There's a high idle CO adjustment on the carb, has anyone ever had to adjust it?

I don't want to go messing up the stuff that's passing by adjusting something else.
 
I did the "rich" check on her again and it's still running rich. I lifted the piston in the carb about 1/16" and the idle picked up speed and didn't settle back down.

The needle is adjusted as lean as it can go and there are no vacuum leaks. The intake/exhaust manifolds are tight.

I read in a spitfire forum you can adjust the floats to help lean it out more. Has anyone ever done this?
 
Often the rich running issues can be traced to the water choke on the ZS carbs. Since yours is a '78 I'll assume that you have the water choke model. John Twist of University motors put out a couple Youtube videos a while back on rebuilding the ZS water choke. Here are they are in three parts.

Part 1
https://www.youtube.com/user/Universitymotorsltd#p/u/90/L5GveCj3Hck

Part 2
https://www.youtube.com/user/Universitymotorsltd#p/u/89/QTFbwcxc5eI

Part 3
https://www.youtube.com/user/Universitymotorsltd#p/u/88/CZ1nr1WroRs

He also has a video on replacing the O-ring in the dash pot.
https://www.youtube.com/user/Universitymotorsltd#p/u/86/hPzB95-paE4

I have two other articles in PDF format that I can send you by email if you like. They go into detail on adjusting the ZS and rebuilding the choke. Not sure how of if PDF’s can be attached here.
 
Rich,

Thanks, I'll take a look at the youtube videos when I get home. We can't access youtube from work. Please do email me the pdf's. I've been battling this problem for about 5 years and I'd love to put her back on the road, legally.

Email to: dale.lisa1@iwvisp.com
 
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