Well,, pardon me for saying so,, but I think youre some kinda Smart!  I mean,, the O2 sensors in the exhaust of a car send a signal, decoded by the computer & used to adjust injector firing, right? I dont see why reading your exhaust cant be used to tell you where you are lean/rich in your rpm ranges,, & under heavy/light loads..
Getting a sensor installed,,, hmmm,,, How about getting a short sleeve cut to put between the header & muffler, so it doesnt have to be permanent? Put it in, make the runs, study the meter, see what the carb needs, adjust ( or not) & pull it off & put it in the toolbox..?
The header is double walled outfit, so, installing there requires cutting thru both,, gonna be messy..
Or, maybe poke a hole in the muffler inlet & have the threaded pipe welded in there? That would keep the exhaust the same length & keep the mounts lining up..
You could take it off & have it done on the lower, inside area & run the wires up the canister carrier & up the frame, under the tank & to the handlebars..

On a more helpful note, this thread shows an install/use of a not-too-expensive AFR meter.  Of course you'd still have to find a good place to mount it.

http://www.thumpertalk.com/topic/876726-no-cost-dr650-jetting-upgrade-%E2%80%...

With the limitations already mentioned about the stock header construction, it would be much more feasible to install near/on the muffler. the problem here is exhaust gas velocity, as the gasses enter the muffler they slow down substantially due to the larger diameter. With installing the sensor at the start of the muffler, you would need to do it in such a way as to subject the probe to a constant, flowing stream of exhaust gasses, in order to avoid false readings from stagnant "pockets" of air. In addition, one would need to avoid impeding the actual flow of air with a blockage in the duct, in which case it is highly dependent on the diameter and length of the sensor probe as well as placement.

another little bump in the road here is that once you get your engine tuned correctly at one Temperature/Air density/humidity level/engine load, your bike may require a different mixture at other atmospheric levels. The good thing is, however, most everyone leaves the jetting alone once it is "close" until it interferes with the ridability of the motorcycle, and only then do we change it. so, with a few pulls on a dyno, we can get the bike running just about perfect for full-load runs at a specific temp/air density and be ahead of the game. At that point, do some "normal" pulls to replicate street riding and ensure the mixtures stay in a safe zone, and rideability is preserved.

Data logging software would be extremely useful here because it's hard enough to whack the throttle open from off-idle to redline in 4th gear and be safe about it, (on the street) than to add in keeping an eye on a multimeter readout and taking notes   Also a much higher level of accuracy is gained, since many digital multimeters take samples at fewer intervals than what is required to obtain high-quality readings. Simply stated, your bike may go from rich to lean to rich again quicker than the meter can react, and you won't notice because it just showed rich for the entire time. Several 'pulls' must be done, in a high enough gear, to ensure accurate readings are obtained over the entire RPM range, And this is all for a strictly Wide-open throttle condition- intake velocity is different at varying RPMs with different throttle openings, such as 1/2 throttle at 5000 RPM vs. full throttle at 1200 RPM. higher velocities mean more pressure differential, which all comes out to more fuel being drawn into the intake. This is why FI is so dang nice... a computer does all these calculations and adjusts for them, based on throttle position, intake vacuum, RPM, ambient temperature, intake airflow velocity, and sometimes even which gear you are in, in addition to adjusting the timing of the spark to go with the different fuel maps.

Rob

sorry to have gone off on a tangent there. I guess what i was meaning to get across is that it should be possible to get a more accurate idea of what your bike needs with a slaved in 02 sensor, than it would be without one. However, you must already be pretty familiar with how to jet a carburetor, to fully appreciate and ultimately be able to use the readings you obtain from the sensor.


My Savage will have a bung installed in the exhaust i will be making for it, just for this purpose. I bet a dial-a-jet would be very useful here for on-the-fly adjustments, hmmm need to order one now for my VM36...

I've looked at one of the instructions for a/f meters and they menstion stuff like pre heating so I think there's more to it then hooking a vom to it and getting a reading.

As to placement... has to be far enough from the end to prevent blow back from the outside screwing up the readings.  The temporary ones have a probe that stuck up past the muffler and have an exhaust extention just as long, all coiled up.

Well on the bright side, if you don't like the looks of the sensor/bung setup, you can always grind it off more or less flush, seal it up and once you re-mummify it, you won't see any difference.

I am surprised you can find a sensor for 25 bucks.  I thought they were around $100 just for the plug, never mind any electronics.

Hopefully you can bribe someone with a welder over there, install it and post some pics. Of course you realize, if you are successful, everyone and their dog is going to want you to try their particular filter/jetting/muffler setup.. hmmm maybe you can charge for that and recoup some of the cost!  

Id have to go to an auto parts store & have a look at the threads on an 02 sensor. Its it pipe thread, youd be paying way too much,, kinda takin it in the "bung" hole, so to speak,, to pay $10.00 for a bung.