Originally Posted by TeeRiver
That is very interesting Grunge. It is cool to see folks digging in and experimenting with the bike.
There is virtually no documentation on how the ISCV is controlled by the ECM, but no doubt there is feedback from the various bikes sensor which explains why the idle speed is being affected by varying conditions (altitude, temp, etc...).
The ECU seems to be able to adapt to a fixed input of air that's not coming through the ISC valve and computes mass airflow just like nothing was changed.
The ISC stepper motor appears to have over-running clutches inside so it will not be damaged by going to full open or full closed. That's what the tak-tak-tak sound is, the stepper motor itself goes "hum".
If that is OK, great!, but good to know, the ISCV for the SV650
can be had on eBay for, like, $15, if you ever change your mind.
Thanks for the link to a used ISCV. I am still studying the one I have to figure out if there is actually anything wrong with it besides the possibility that it has some gunk concealed in the passages or that the plunger shaft tends to vacuum stick to the front cylinder port when the throttle is rolled off.
WeeBeliever is an engineer who was riding a Vstrom about eight years ago and he did an excellent analysis that on a Vstrom website. He says that the steeper motor has about 125 steps and that it moves the plunger about 1 millimeter when the key is turned on and that it moves open about 2 mm and closes again during a normal shut down. 125 steps means that the plunger
moves about .125" at full excursion and fixing the ISC to step 58
using the SDS moves the plunger about .058" At normal engine start the
plunger would be at about step 40. WeeBeliever made up an adjustable plunger so he could measure the stroke of the plunger while the ISC stepper motor was hanging out of the ISC body but I had already been considering
making up an inexpensive bypass air valve.
The Grunge Ryder Manual Idle Speed Control Device doesn't have the automatic fast idle function of the Mikuni ISC, so if somebody needs to adjust the Raindrip valve to achieve a certain RPM on cold days, the valve can be installed to stick through the triangular hole in the right hand side of the frame under the sticker that says idle RPM is non-adjustable.
However, if the rider lives in a mild climate like I enjoy here in California, the Raindrip valve can easily be attached to the bottom of the airbox where the ISC tube takes filtered air from, and the valve can be set to 1/4 turn open and left there until it's time to synch the TB's again.