The first photograph shows work in progress. It's actually nearly done, but I'm waiting for another LED to arrive before drilling the final holes. Shortly after the LED arrives this will become the upgraded Mark II "universal" instrumentation package that I've designed to clamp to just about any set of handlebars. What the photograph doesn't show is brazed underneath is an array of seven nuts to allow the clamp, shown in the second photograph, to connect to the platform as close as possible to the center of gravity irrespective of the location and orientation of the clamp on the handlebars (e.g. clip-ons are nearly horizontal, the unobstructed segments of ape hangers are nearly vertical, and typical handlebars are somewhere between these extremes).
The Manfrotto "Super Clamp," repurposed from its camera holding tasks, is perfect for this. It has a rated capacity of 33 lbs. but only will be holding less than 3 lbs. including the Manfrotto universal joint. Together they can position the platform in the best location on just about any bike, as well as hold it so it doesn't vibrate any more than the handlebars themselves do.
Mounted on the platform will be an Innovate MTX-L air/fuel gauge along with a data logger that will record data from that meter as well as from a "universal" throttle position sensor (that also clamps to handlebars), tachometer, accelerometer, exhaust gas temperature (EGT) sensor, and knock sensor. As mentioned previously, engines "feel" like they're running well with Air/Fuel Ratios anywhere between ~10:1 and ~15:1 so accurately adjusting the several circuits and jets in a carburetor for either max. h.p. or max. fuel economy requires just such instrumentation.
For someone who doesn't want to permanently install a wide-band sensor in their vehicle Innovate sells an "exhaust clamp" (sampling attachment) that inserts in the end of the exhaust pipe to sample the mixture. The next photograph shows the sampling attachment that I bought with my original meter.
The design is like a Pitot tube, with the exhaust flow past the holes in the side of the shorter tube reducing the pressure and drawing the mixture in the end of the longer tube, past the sensor, and then back out again through the holes in the shorter tube. However, this sampling attachment comes with the warning that it probably won't work on a single-cylinder engine (or a twin with separate pipes) because air is sucked back up the exhaust pipe some significant distance on each cycle. Unless the tip of the sampling unit is further up the pipe than that point, it will give bogus readings. Which it does on my motorcycles. I overcame this problem with a "Bunsen valve" arrangement I discussed some time ago, but it wouldn't be an ideal solution for many people.
So, how far does air get drawn back up the pipe? Despite the relatively short pipe currently on my Catalina I know from the behavior of the meter that the location of the sensor doesn't suffer from the air reversion problem. It happens that the Catalina's "silencer" doesn't have anything in the center of it so it's a straight shot all the way to the bend in the header, just past the "permanent" sensor. Since the sampling unit is pretty much useless as-is, I extended it by 10" so it now reaches to the location seen in the photograph. This will let me answer the question at the beginning of this paragraph.
As a result of my instrumentation upgrading process I now have a second Bosch sensor and a separate control unit for it. Which means I can have my upgraded Mark II instrumentation package in place, but also use the elongated sampling unit to determine the depth into the pipe where reversion no longer is a problem. With a helper, AKA long suffering wife, I can check this from idle up to at least a few thousand rpm while the bike is sitting in the driveway. Note that I'm not suggesting determining the jetting this way, since it wouldn't be under load, only determining the depth of the reversion.
This elongated sampling unit has two separate functions: as a test probe to determine the depth of reversion, and to determine the AFR on the road without having to modify the exhaust pipe or use a Bunsen valve. However, the latter relies on the design of the silencer so it won't work on all bikes. For example, it fits up the pipes of a Matchless G80 and Triumph 500, but not a Trident. Still, for bikes where it will work it is an alternative to either a Bunsen valve or permanent modification of an exhaust pipe.