Living with the TORS switch

Often incorrectly referred to as the Throttle Position Sensor (TPS), the TORS switch can be found in your thumb throttle housing. The purpose of the TORS switch is to shut the KTM ATV down in the even of a stuck throttle situation.  This is accomplished by using 2 arms, one which is connected to the throttle cable, and another which is connected to the thumb throttle itself.  The second arm has a small spring to make it return, and when you push the thumb throttle, it pulls on the arm which is connected to the throttle cable. In the event of a stuck throttle, when you let go of the thumb throttle, the small return spring will make the thumb throttle return to the closed position, which will also close the TORS switch.  At this point, if the TPS sensor is telling the CDI that the throttle is open, the CDI will assume the throttle is stuck and kill spark.

This is nothing new.  Most ATVs have a similar system. What makes the KTM unique is KTM’s decision to check the system each time the CDI was powered up.  On other ATVs, eliminating the TORS switch is easy, since all you have to do is make sure that the switch is either always opened or always closed, depending on what the CDI needs to see to give you spark.  Unfortunately, it is not that simple on the KTM, which causes a few issues when people try to bypass it or start on the gas.  However, once you understand how the TORS switch actually functions, living with it is really no problem.

First off, each time you power up the CDI, it must see the TORS switch CLOSED before it will give you spark.  However, it also needs to see the TORS switch OPEN in order to rev.  This is why the throttle should always have a little play in it.  That way when you put pressure on the throttle lever, you open the TORS switch before you begin pulling the throttle.  As stated above, if your CDI sees throttle position too high and the TORS switch closed, it will kill the engine.  As an aside, this is also why it’s possible to turn the idle up too high to allow the bike to start.  You can actually open the throttle up with the idle screw far enough, that when the CDI sees the TORS closed, it assumes you have a stuck throttle and shuts the bike down.

All of this may sound like a pain, but it really isn’t.  As long as you keep the appropriate play in the switch, it is essentially maintenance free, and has been COMPLETELY trouble free for me as long as I’ve been on KTM quads.  Here are a couple of tricks you may enjoy though:

Starting on the gas:  This is possible with the KTM, and makes for GREAT dead-engine starts with a 24V system!  What you have to do is turn the key on and power the CDI up.  Once it sees the TORS closed, you can start the bike and rev it up to half-throttle or wherever you want to start it.  Next, kill the ATV by pushing down on the orange kill switch button, WITHOUT releasing the throttle. Since this kills the ignition WITHOUT powering down the CDI, the CDI has still satisfied it’s test of the TORS because it has already seen it closed once.  Leave your thumb where it is, hit the start button and off-you go!

Removing the TORS return spring:  Believe it or not, the little spring in the throttle housing is actually a significant contributor to throttle effort.  I have removed this spring on my ATVs, and the difference is DEFINITELY worth the minor inconvenience that comes with it.  Remember that the TORS needs to be closed at least once to get spark.  Therefor, as soon as you turn the key and power up the CDI, you need to pull the throttle lever back to the fully closed position to close the TPS switch.  From there on, as long as you don’t power down the CDI, the bike operates completely as normally.  I’ve heard of folks tying a waterproof kill button or something else into the TORS switch, turning the key, hitting that button, and going about their business, but for me, the little microswitch in the throttle housing has been MUCH more reliable than any start button I’ve ever run, so I just leave the existing system in place and remember to pull the lever back the first time I turn the key.

Eliminating it with another CDI:  It is possible to eliminate the TORS switch entirely using a 450SXF dirt bike CDI from one of the RF4 bikes.  In addition, the VORTEX X10 CDI does not look at the TORS switch.  I’m not sure about the Dynatek, but will update this post if I hear one way or the other.  I’d anticipate that they don’t bother to look at it.

Eliminating it with a relay:  Another solution is to tie a relay into the start button that closes the TORS switch when you hit the start button.  Since seeing the TORS switch closed will allow the CDI to give you spark, this solution will work.  It does however eliminate the possibility of starting the bike on the gas because as soon as you hit the start button, the TORS switch will close and the CDI will assume you have a stuck throttle cable and kill spark.  Other issues with this setup include an inability to bump-start or kick-start the bike if you haven’t hit the start button first to close the TORS switch.