Been keeping up with the “Halvors O2 tuning” thread with interest. The thread sorta morphed into a tuning session so I thought I would start a new topic that addresses the ox sensor installation directly.

I went on EBay and bought an “Auto CAR 2"52mm Digital Color Analog LED Air/Fuel Ratio Monitor Racing Gauge” for $35.55 including shipping from somewhere in China. In less than 10 days, I got a package in the mail.

The gauge has a blue fluorescent digital display and colored LEDs arranged around the circumference. They show different colors depending on the ox sensor output.

I hooked up a variable power supply through a voltage divider to simulate the zero to 1 volt output of a narrow band ox sensor. The numeric readings ranged from 20 at 0 volts in, to 10 at one volt. At .4 volts out the reading was 16.1 and at .6 volts it was 14.1. So the stoichiometric 14.7 would probably be around .55 volts.

I had an old ox sensor that I removed from one of my vehicles. I heard that you could test them with a propane torch. So I hooked up the gauge to a 12-volt battery and connected the input to the ox sensor output. I also ran a ground wire to the ox sensor.

When I first applied power to the meter with the ox sensor cold it read 20, which is dead lean. As I heated the ox sensor with a torch the voltage from the ox sensor went up and the meter reading went down. I think it got to 13.5 or something like that at the highest.  Doesn’t matter the exact numbers just that the system is working. One would have to apply a fudge factor possibly, but the gauge should be close enough for tuning purposes.

Now I need to weld a bung on to the savage exhaust or maybe figure out a way to mount the ox sensor inside the muffler outlet.  I’m in the process of transforming the bike from a cruiser to a street tracker so it really isn’t together enough for testing.

Hopefully somebody else on the forum is ambitious enough to set up a bike with the equipment. I’m just showing you how to do it on the cheap. You should be able to find an ox sensor from most any late model car in the junkyard. It doesn't have to be new, though the older well used ones tend to slow down in response as they age. If one held the throttle at a fixed setting  the reading would eventually stabilize and at least you could discern a general rich/lean trend.

John in Kalifornia





Ox sensor cold- lean condition


Ox sensor heated up. Note flame and meter reading

More information:

The ox sensor has to be at an elevated temperature to work correctly. There are heated sensors that come up to temperature more quickly, mostly for emissions control requirements. You can't just hook up the heater, it has to be cycled on and off so it won't burn out. I think it's better to go with a one wire unheated sensor and accept that it will be sensitive to exhaust temps.

There is a "FAST™ EZ Clamp-On Tailpipe Wide-Band Sensor Mount Kit" that fits inside the tailpipe for temporary use when one doesn't want to modify the vehicle. This may be the way to go. Just an idea, will need to be modified for a motorcycle application.

John in Kalifornia