I never wanted to deal with trying to butt dyno a bike, so I put a bung (actually four, one for each runner) into my exahust to get a read out on the air/fuel ratio of the engine. You'd probably be safe with one sensor as carb screw settings rarely ever change between cylinders.
I bought a bosch lsu 4.9 wideband sensor from ebay and a
SLC free wideband controller
. If you get the sensor used, the whole thing will run you about $70. If you wanna go cheaper, you can typically find the controller as a kit or just the boards on ebay for cheaper though your electronic skills need to be pretty good to go that route.
The other option is just buying a new wideband sensor kit from AEM or Innovate, but these can be pretty pricey at ~$200. You can find these for ~$100 used on forums and maybe ebay. These kits are just different controllers but use the same 4.2 or 4.9 bosch wideband sensor.
After you get all that setup, its just a case of running your engine, looking at the reading, and tweaking the carbs until the AFR is where you want it. 14.7 is stoichometric and you dont want to go above that: you'd want to be around here for a cruiser. 13.3 or so is best for power.
Different throttle positions have different purposes. In the light throttle range for cruising I find I end up around 14. At the extreme end of the power range I end up sweeping through 11.5 to around 13 as the rpms reach redline. I have a thread here somewhere with more details, but it was so long ago, I think the images are gone.
I've only afr tested mechanical carbs. CVs might behave differently.
My previous post was autocorrected "precise" was changed to "pre use".
A friend of mine has been tuning his CV32, 1984 GPz550 with 12:1 Pistons, and Web Camshafts (410 lift). He says the Innovative LC1 has helped him better understand tuning. He only has one sensor to the mid-pipe. From where he though it was tuned, wasn't close when he added the wide band. I bought this an LC! from Innovative off Ebay, but have yet to install it. CV Carbs are different running than that of mechanical, and tuning is different.
He says tuning the carbs for the street is ideal, as we are not even close to constant full throttle on the street. Cruising, we are about 1/8 throttle opening as Lou says.