Originally Posted by
Tork
When backing out the idle screw, I monitor the TPS Degrees value since it's directly related to the TPS reset procedure. The value will decrease as the throttle plate closes (indicating the opening amount in degrees). When the throttle plate hits the mechanical stop, the plate is prevented from closing any further, and the value should stop decreasing as you continue to back out the idle adjustment. However, there may be some friction in the TPS sensor, throttle plate shaft, etc. that makes the plate hang open a tiny bit. Snapping the throttle open/closed at this point helps overcome that friction and help force the plate closed. Using some carb cleaner in the throttle plate area can be useful prior to the TPS reset, especially if the throttle plate area looks dirty. I blip the throttle and back the idle out a quarter turn a few times just to make sure that the TPS Degree value bottoms out and no longer decreases, indicating the plate is truly closed. This is the point at which the TPS should be reset. Ignore the actual value while doing the TPS reset procedure - You're just looking to verify that the value stops decreasing. Make sense?
I've seen posts from folks who mistakenly stop backing out the idle adjustment as soon as the TPS Degree value reaches zero, and hit reset. If the TPS sensor is worn, or the previous calibration was borked, the throttle plate may still be slightly open, even if the displayed degree value says '0', so zeroing the TPS at this point would just produce another TPS mis-calibration. In this case, if you were to continue to back out the idle, you'd notice the degree value go negative (-0.5, -1.0, etc.), indicating that the plate still had more to go before it was truly closed, and that the previous calibration was indeed off. Remember, when doing the TPS reset, the goal is to calibrate the electrical 'zero' point to the mechanical condition where the throttle plate is completely and truly closed, so using the degree value as described above is a useful tool to help tell you when it has reached the mechanical stop and is ready for reset. Just be careful and only back out the idle a bit at a time and only enough to verify that the plate is closed. Back it out too much and you risk unscrewing the idle cable completely out of it's threading and getting it back in is a pain in the ass. Also - putting a little grease/lube on your idle adjust cable threading can help make your TPS/idle adjustments smoother (less twitchy) and help keep the cable from binding and breaking due to corrosion.
After you hit reset, bring your TPS Degrees up to about 5.5 - 5.6 degrees, adjust the idle to about 1000 rpm, start the bike and take it for a short ride to bring the engine up to temp and closed loop condition (temp above 160C, cold start enrichment = 100). Make your final idle adjustment and you're done. If the RPMs hang a bit at stop lights/signs, just back off the idle slightly until it returns normally.