Introduction & O2 Sensor Questions

[Neil Poersch/MTSCom/MTS]

Hello everyone,

I stumbled across your web page while surfing the net for info on 
oxygen sensors, was impressed by the good info and thought that 
I might learn more by joining your mailing list.

I am the proud owner of a somewhat obscure brand of Italian-made 
motorcycle, a Moto Guzzi.  I am constantly modifying it to improve
performance.  This past winter I bored out the carburetors from a
30 mm to 36 mm throat.  This of course meant that I had to revise all
the jetting in the carbs to accomodate the increased air flow.  I  did 
this using the traditional method of observing spark plug color.  This
of course takes a lot of time so I thought  a better way might be to
monitor the output voltage of an oxygen sensor.  I am aware of the
unit which K&N sells but I thought it was very over-priced for what you
get.

I purchased a universal replacement O2 sensor (made by or at least 
packaged and distributed by KEM Automotive Products), machined a 
fitting and TIG welded it onto the crossover pipe on my exhaust.

I find that under normal running conditions I typically read about
0.9 to 1.0 volts from the sensor. From what I read about O2 sensors
this should indicate a very rich mixture however the engine seems to run
quite well and the plugs show a light tan colour.

I believe the sensor does respond to lean mixtures because when I
deliberately make the idle mixture overly lean I read 0.3 to 0.4 volts.
Also when I am running wide open throttle on the highway and snap the
throttle shut I momentarily read 0.1 to 0.2 volts until the carb responds to
the new conditions.

After all this rambling I guess my question is has anyone had any
experience in using an O2 sensor for monitoring fuel/air ratios?  Also
does anyone have any info on what the output voltage curve versus 
fuel/air ratio should be?

Thanks.  Look forward to hearing from you.

Neil