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2013 YZ 250 Idle Problem

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I have a 2013 YZ 250 with about 10 hours on it and I ride in elevations that range from sea-level to 5500 feet approximately.

If I set my idle in my garage, near sea-level, then go ride at the higher elevations, the bike isn't idling or even near idling. If I set the bike to idle at the higher elevation, when I come home and fire it up, it's idling so high it will blow up if I don't shut it down.

Again, this isn't a small idle adjustment that I have to make from place to place—it's numerous turns with the adjuster screw.

I'm stock jetted with an FMF spark-arrestor—I'm too rich, I get a substantial amount of spooge but that shouldn't be creating this huge idle discrepancy.

178 main

N3EW needle at the 2nd position

#50 Pilot

My air screw is 1 and 3/4 out

Any ideas on what I should start to look at or do?

Over-oiled air fliter from the factory maybe?

Air leak?

I don't really know where to start...

Edited by BlindSide

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If your going higher than 1000 ft above sea level then you should be rejetting to suit the change in higher altitude.

I think its something like every thousand ft you go up in altitude you drop one size down on the main,pilot n playing with the needle or clip positions maybe,I'm sure someone here knows this formula and will chime in.

Higher up is lesser oxygen,more fuel there runs too rich so leaning it out compensates for that,then the opposite way when you go lower in altitude.

Anytime you go up or down in altitude you will need to set the air screw also

Hope this helps

Edited by ozmx

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Weird, my buddy has a 2012 model and he hasn't touched the idle since bringing it home—riding all the same places. According to the YZ CF factor jetting chart, I was spot on for yesterday's elevation and temperature...granted, it's only reference. I'm sure I need to compensate some for the spark arrestor. I know it's rich up there but the discrepancy in idle is huge when I come home.

I had 2-strokes in the 90s and don't remember idle issues like this.

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Set the squish somewhere between 0.045-0.050" and run this @ sea level:

Stock float level; 32:1

50 Pilot

#8 Slide (Kawasaki Part No: 16025-1217 - $60ish)

N3EJ Needle, 2nd clip

#50 Power jet (stock)

175 Main

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The stock pilot in that bike at just about any elevation is guaranteed rich. There are lots of way to check the pilot and adjust the air screw but Slavens racing has the easiest way that I know of. Go look up his website and he has a good video explaining it. The main is also rich and the slide definitely needs to be changed to an 8 but that doesn't really have any bearing on the idle. The yz 250 that I have is the worst idling bike I have ever owned. I don't know why nor have I ever worried to much about it. I just learned to ride with a bike that doesn't idle. Actually is a helpful thing to learn.

When you say it idles high at home. Is that just when you fire it up with the choke on, or is it even when it is warm. If it is just with the choke on that if fairly normal. I think its a sign your air screw is set lean, but don't remember.

The spooge probably has more to do with the oil you are running and where you ride. If you ride tight muddy woods or other slow stuff your motor will never get hot enough to burn some of your higher quality oils. There are oils that burn at a lower combustion temperature and will help it. Maxima Super-M or Motul 710 both work well. Maxima is alot easier to find.

Unrelated but if you do switch slides make sure you get the cable holder also. Running the Kawi slide with a Yamaha cable holder is asking for a broken needle.

Edited by Willwater

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In order to jet a bike, it has tobe at running temperature. And you can only jet for the moment where you are riding, You cant do it at home than hope it runs just as well 5000 feet higher.

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you know if it is that new i would take it back and get them to figure it out or atleast ask them

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