"Here's probably the best description of "how to" around. Taken from the FIM website.
The only addition i would make would be the backing off of the balance bar mentioned above. You MUST set the TPS to the front butterfly being closed, not the rear holding the front open.
• Set the Throttle Position Sensor on the throttle shaft. To correctly do this you must:
o Completely back off the idle stop screws on both throttle bodies.
o Use the Mathesis tester or a Digital MilliVoltMeter to read the throttle sensor voltage. To do this you should tap the butterfly with your finger to ensure that the butterfly is completely closed against the body. Then you turn on the ignition and measure the voltage on the throttle sensor:
P7 or P8 ECU: Pins 11 and 17.
1.6M ECU: Pins 16 and 30.
1.5M ECU: Pins 22 and 11.
o If the sensor does not read 150mV Plus or Minus 2mV then you need to adjust it:
Slacken the lock screws on the throttle sensor using a screwdriver or 7mm socket.
Carefully move the sensor whilst reading the voltage.
Retighten the lock screws a little at a time, each time reading the voltage and adjusting the sensor.
Note that you should probably overshoot the reading by about 5mV on slack screws, because when you tighten them the reading will change by about 5mV.
Repeat until perfect. This takes a lot of practice.
o The factory manuals specify +/- 5mV but we feel that this is not accurate enough. many owners will attest to the difference in performance when the sensor is set perfectly.
o Re-set the throttle stop screw (or screws) so that the engine idles at around 1200 rpm. This is not a final setting for the stop screws, merely a step in the procedure. Typically this will produce a voltage of around 300mV on the TPS. This value is completely arbitrary and is not important. Many people misunderstand the factory manual in this regard and will try resetting the TPS until they get 1200 rpm idle and exactly 300mV on the sensor. THIS IS WRONG !!!. The actual voltage on the sensor at idle is irrelevant to correct sensor positioning on the throttle shaft. Trust Me !!
• Synchronise the Butterflies:
o Close the airbleed screws completely by adjusting CLOCKWISE. If you don't do this then the throttle vacuum will still reflect any air passing through the bleed channels and the butterflies will not be perfectly synched.
o Attach vacuum gauges to the manifold port on each cylinder and run the engine.
o Adjust the throttle butterfly link shaft until vacuum is identical.
o Rev the engine and confirm that vacuum tracks on both cylinders throughout the throttle and RPM range.
o Re-adjust the link shaft until satisfactory results are obtained.
o Do Not adjust the throttle link shaft after this point.!!
• Set the IDLE Balance by adjusting the airbleed screws counterclockwise and confirming that the vacuum is identical for both cylinders at idle. You can rev the engine and observe vacuum tracking through the rev range, and then observe idle vacuum restabilising. NOTE Since the airbleeds are designed to iron out any irregularities in the throttle's function, by their nature there is no default setting, unlike the idle screws on a carburettor. If anything the default setting is fully closed. Airbleeds can also be balanced using a 2 channel CO meter. In this case, just adjust the bleeds until both cylinders have the same CO.
• Adjust the IDLE Mixture. Finally you get to set the CO Trimmer ! This will affect both cylinders by the same amount, so you need to set the airbleeds first. A typical CO figure for idle is 4% to 6%, but automotive regulations usually specify a CO of under 1% to meet emmissions standards. A V-twin will idle very poorly if the CO is set below 1%, so if you are really bothered try a setting of about 3%. Note that you may need to finesse the airbleeds at this stage.
• Adjust the IDLE RPM. Set the idle rpm at the manufacturer's figure (usually 1100 - 1200 rpm) by adjusting the throttle butterfly stop screw (or screws). We recommend 1200 rpm for Ducatis and Guzzis, possibly 1500 rpm for Ducati 996SPS models.
• Finally, note that the last three steps are usually repeated until an acceptable balance of Idle Balance, Idle Mixture, and Idle RPM are obtained. This is normal. Do Not adjust the throttle synchronisation link shaft once it is set in the early stages. If you do this now, you will need to go through the entire sequence again.
So hopefully you will have an engine which now idles, accelerates, and delivers full power faultlessly. Again, if you are not confident about all of these steps, then we suggest you use a dealer who has the skills and equipment. It is not worth adjusting the CO trimmer unless the entire sequence is followed without skipping any steps."
I know this is an old post, but I would like to add a comment. This should be an ABSOLUTE LAST RESORT to cures for idle problems. Look at valve clearances, valves, air lines, look for air leaks, balance the throttle bodies, adjust the CO, etc. before you do this. The reason is that the TPS is a really non-linear device at the closed position. Depending upon how you close the butterfly, (let it slap shut, roll it slowly closed, roll it hard to the stop) you will get readings on a DVM that vary by way more than the tolerance being specified. I struggled for a long time with this, and when it was all said and done I am pretty sure the TPS had nothing to do with the original problem.
Also, the Tech Research software will let you see what the ECU thinks the TPS position is, and I think that works better than a DVM on the connector pins. If the CPU says 3 degrees, then the air/fuel map will be starting in the right spot no matter what. The software is less than $200, and worth it.