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Discussion Starter #1
I explained how I came to build an inexpensive manual idle speed control device in an earlier thread.

Since the stepper motor operated ISC wasn't passing the same amount of air to the front and rear TB's, I decided to road test my 2008 SV650S with my manual idle speed control device installed.

I set the manual valve so the engine would idle at 1625 RPM when the coolant temperature was about 200 degrees.

This allows me to shift gears more like I'm riding an I-4, there isn't so much lurching and trepidation about downshifting with the idle speed at 1625.

Then I did a 175 mile sport ride with altitudes varying from 450 feet above sea level to 3000 feet ASL.

Again the motorcycle was a pleasure to ride, with much less lurching and excessive engine braking.

Today I rode up to 7200 feet in the local mountains. The weather was mostly cloudy and the density altitude at my high point was actually closer to 9000 feet because of the high humidity and cooler air.

The engine idle speed was affected by ambient air temperature, engine coolant temperature. It ranged from 1250 rpm when the engine was cold and rose as high as 1600 RPM, but the ECU took the temperature and pressure variations in stride.

I did hear the stock exhaust popping three or four times at 7200 feet.

But it looks like the Grunge_Ryder Main Idle Speed Control Device has found a permanent home, since the price of a new ISC varies from $175 to $225.:vroom:
 

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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...). 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.
 

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Discussion Starter #3
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.

:vroom:
 

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Thanks for the extra tech detail, Grunge! I was not aware of the good detective work WeeBeliever had done.

This looks like a fun next project to discover more secrets about the venerable SV. It would be nice to know exactly what the SDS does during throttle body sync procedure, lots of folks have asked that question. Is there a way to do throttle body sync on the 2007+ SV without using the SDS tool? Maybe you know?
 

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Discussion Starter #5
:vroom:

The SDS freezes the ISC plunger at step 58 so the valve won't move to adjust the idle speed as the mechanic tweaks the two throttle body air screws.

The SDS window does display some good info, like coolant and inlet air temperature and inlet air pressure, and I suppose that one could synch the two TB's by watching the numbers in the SDS window without even hooking up vacuum gauges.

However, someone who is knowledgeable about simple homebrewed instruments can make up a mercury manometer to get a direct reading in inches of mercury vacuum.

An SV650 cylinder should pull about 7 inches of mercury vacuum which equates to about 11.02 psi manifold absolute pressure and 3.5 psi vacuum at idle

The height of the mercury column will be about 7 inches if one is using a well manometer where the cylinder is pulling against ambient air pressure.

But most mechanics won't be interested in knowing what vacuum the cylinder is pulling if they can just match two columns of liquid in a u-tube manometer

The reading in a u-tube manometer will be half that of a well manometer, but the fluid used will have much less density than mercury, which has a specific gravity of 13.58 compared to water which has a specific gravity of 1.0.

Hydrocarbon fluids like oil or ATF have a specific gravity of about half that of water, so the height of a column of hydrocarbon liquid in a well manometer will be about 27 times as high as that in a U-tube manometer which will preserve its liquid as long as both ends are connected.

While the old standard for synchronizing carns with a set of Carb Stix was to keep the dancing columns of mercury within 1 centimeter of each other, one might see a difference of 27 centimeters between columns of ATF and the readings would still be in spec!

Anyway, to synchronize TB's using the Grunge Ryder Manual Idle Speed Control Device, one simply starts the engine and warms it up to 176 to 212 degrees, then hooks up the
GRMISCD to the vacuum ports and adjusts the air valve to make the engine idle at 1200 RPM.

Then opening the air screws equally on the TB's just makes the engine idle smoother and the two columns of mercury wil dance up and down very little as the RPM increases to about 1300 RPM.

Then the GRMISCD can be disconnected and the ECU-controlled ISC can be hooked up again, and what does it know?

Nothing new.

If nobody has used the active control program of the SDS to change its set point, the engine will idle at the preset RPM
 

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... The SDS freezes the ISC plunger at step 58 so the valve won't move to adjust the idle speed as the mechanic tweaks the two throttle body air screws.
So, if a throttle body sync is performed without using the SDS tool to freeze the ISCV plunger, and so long as the rpm remains basically constant, what would be the problem?

No matter the position the ISCV plunger, it bleeds air equally to both cylinders, no?
 

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Discussion Starter #7
The ISC is supposed to supply equal amounts of air to the TB's, but the firing order of a V-twin may be sucking the plunger over to the front cylinder orifice under closed throttle, or the ISC may stick due to oil build up inside it.

The spec for idle rpm is 1200 to 1400 rpm.

What if the engine won't smooth out below 1400 RPM?

If the ISC is working correctly and regulating air flow equally to make the engine idle at the preset RPM of 1300 rpm and the mechanic opens the air screws to make the engine idle faster, the ISC should react to reduce air flow and slow the idle RPM down.

If the TB's were really misadjusted by some overly enthusiastic mechanic or the air screws are dirty or the ISC is clogged up with oil from the crankcase breather system or the TPS is erratic, the home mechanic won't be able to easily synch the TB's.

The lurchiness when rolling off the throttle which made me believe that my TB's needed synchronizing was actually caused by the ISC and the TPS.

I researched the TPS problem and found that Suzuki changed the part number.

So I googled the new part number and found some discusssion on other forums.

Some Vstrom riders were talking about the erratic TPS sensor on their machines causing stalling.

They said that the TPS was sensitive to heat but that the change in voltage wasn't high enough to cause the ECU to display a fault code.

:vroom:
 

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Hmm... That makes me think I might need to replace the TPS on my 06. Intermittent issues after 10 minutes on a freeway, and only in the evenings, never the mornings...

And by intermittent, I mean it hasn't done it since last Tuesday, and before that it had been a month or two...
 

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Discussion Starter #9
The K6 uses a different part number TPS, but it may be sensitive to temperature changes.

Somebody on a Vstrom forum said that the temperature sensitivity of the TPS could be
demonstrated by spraying it with some kind of aerosol coolant liquid commonly used in the electronics industry.

It wouldn't surprise me a bit if the TPS screwed up if sprayed with Freon or starting ether..
 
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