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[TheShaggyDA]

I thought the lower the voltage the leaner it is, rather than richer :-






from Instructables - O2 tester circuit

[Gwilly]

Just as long as your not running too lean at higher rpm wide open throttle..

Ball park can be obtained with plug chops and general feel in the saddle but i think for serious tuning a half hour session on a DYNO with printout copy will provide evidence of what is going on across the full range..

Repeatable and comparable after adjustments, not sure if i could trust or even remember sets of LED's at 70mph.

[Rattlebattle]

You may well be right ShaggyDA; it's not something I've studied. It's only a cheap marrow band sensor on an RE EFI and a pretty crude system, certainly compared to modern cars. I'd tune the carb empirically in the time-honoured fashion (or use/borrow a colourtune - not carbtune as I said earlier. Good enough I would have thought.

[Creaky45]

You're right Shaggy. I got that backwards. I might try hooking up the heater wires and see if I get a different reading. Will let you know.

[Creaky45]

I am finally getting somewhere. The type of sensor I am using comes out of a car and has 4 wires which means the 2 for the heater MUST be used. It does not get hot enough to function correctly with just the exhaust gasses. I connected the heater which is about 3 ohms and draws around 1 amp at first then drops to .7 amp after a few minutes. This made all the difference and now the leds show I am actually almost correct with the mixture at all throttle openings. From a cold engine it takes at least 5 minutes of running before I get the correct readings. It is quite sensitive in that I can turn the idle mixture screw just a 1/4 of a turn and see a change on the gauge. I am told you can get a single wire sensor which would no doubt be calibrated in a different way so as not to need that extra heat.