zenith carbs

[pbailey@qnet.com]

Happy New year everyone!! I have a couple of questions..
I'm losing oil in my ZS carb what o-ring do I fix and is it very hard to 
change? 
Also I read in my MGB service manual you have to adjust the carb using a CO 
meter and it said the CO should be 5 1/2 percent I have a CO meter that reads 
in 
PPM what PPM does 5 1/2 pct equate to? Thanks in advance
Pat  79"B"