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Idle & Cold Start Screw adjustment how-to | late model KTM EXC dirt bikes with EFI systems

Idle & Cold Start Screw adjustment how-to | late model KTM EXC dirt bikes with EFI systems

I pointed out in my first ride video for my KTM 500EXC-F that the bike had a tendency to flame out quite a bit more than I thought it should, and after adding the GET ECU, I had a few issues restarting the beast. Both situations were pretty frustrating, and of course I caught them both on video.

KTM split the duties of the perfect cold start mixture and the fully hot idle, kinda like what McDonalds did with the McDLT back in the 80’s. Instead of a styrofoam box however, KTM keeps the hot side hot with the idle adjuster, and the cold side cold with the cold start knob, if I am going to complete this horrible metaphor. KTM’s design is actually pretty brilliant… if you have them adjusted correctly.

I discovered that when I picked the bike up from the dealer that the idle screw was all the way in, which was not anywhere near to close to where it should have been set. Unfortunately I discovered this long after I had adjusted the idle by using the cold start knob, which as the name would imply, should only be used for cold starting and not what I did.

The yellow-knobbed cold start adjuster works by acting as a choke to provide the appropriate air/fuel ratio for that initial start of the day, and is activated by pushing the adjustment knob in. When you apply the throttle the knob automatically pops out, which if it (and the idle screw) are adjusted correctly will allow you to go ride. To adjust the cold start feature you twist the knob which conveniently clicks into the next position, kind of like your shock adjuster. I was using this as a means to get the idle where I wanted it, which as I already mentioned was a mistake.

What I should have been using was the aptly named idle adjustment screw, which is the red knob on the top that does not click into position, but allows for more of a fluid adjustment by being spring-loaded. The owner’s manual suggests that the bike should idle at around 1800rpm, which I feel is a little high, so I set it by ear just a bit lower.

It should be noted that in order to get the idle set to your liking you will need to set it when the motor is at full operating temperature, and in order to set the cold start knob dialed in, the motor should be cold.

As we all learned in kindergarten, two wrongs don’t make a right. Trying to correct the dealer's mistake of leaving the idle adjuster all the way in by twiddling the wrong knob is just further proof that most of what you need to know as an adult you learned when you were five, it is just applied differently.

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