I have an 02 gauge on my bike. When it is indicating any number such as 20.0 (maximum range), 10.0 (Minimum range) or anything in between the number displayed on your 02 gauge means a RATIO of that number to one and NOT say 20%. Example: the gauge indicates 14.7 this means the ratio of air to fuel by weight is 14.7 to 1 and not 14.7%.
Here is a link for a more detailed description of air fuel ratios:
http://en.wikipedia.org/wiki/Air-fuel_ratioThe 02 meter mounted on the bike helps me get the carb dialed in very close to optimal then I do all my fine tuning on a dyno. This gets the mixture perfectly dialed in every time. takes about 1-2 hours of dyno time at $85.00 an hour at the local Harley dealer.
The reason I have an 02 meter permanently installed on my bike is I play with different cam profiles, mufflers and carbs all the time. The 02 gauge lets me know if the mixture is getting off to much and I need to re-jet.
FYI...I have a highly modified engine and the jets I had to order to get this carb even close to right have cost me more than the original price of the carb.
My A/F ratio is currently running at 13/1 at 1/4 throttle cruise, 10.3 at idle and off the gauge over 20/1 at WOT!
I am getting 60+ mpg and I need to order more jets, particularly needle jets...these cost almost $20.00 each.
My engine is a 97mm high comp motor with a high lift web cam, ported cylinder head, stock head pipe and custom muffler.
main Jet: 210
needle jet: Q0
Pilot jet: 10.0
UFO
Torque wing
The guy at the Harley dealer freaked out when he saw I had a 210 main jet in this engine...he says he doesn't use jets that large on 110 HP Harley's....I told him this ain't no Harley...this is a SUPER THUMPER!!
When I am done with the dyno I will post all the results including final jetting.