That's a neat little co analyzer Bert... what did it cost you if you don't mind me asking... if it's accurate, will give you a lot of info on air / fuel mixture combustion efficency... I have one of snap-ons handheld 5 gas analyzers, only issue with using it on premixed fuels, you have to protect the probe end from the oil contaminating the tip... I tried it on the GF40 with the exhaust tube placed inside a glass jar and the probe end separated by some cotton wool... it seemed to work well, just the cotton slowed down the sensors response time, but for carburation, not really an issue.