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2017 YZ250FX Idle Increase When in Gear

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Hello All,

Grabbed a new left over 2017 YZ250FX a few months back.  I haven't ridden it yet, but finally got it out of the garage today.  Pull the starter knob/idle adjuster, lit it up, let it warm up, pushed the knob in.  All good.

It was idling slow (1500-ish rpm), so I turned the knob until it was about 1900 rpm (which, btw, was about as fast as I could get the idle set--even all the way clockwise).  Pulled the clutch, put it in gear, and the idle jumped to 2400 rpm!!  Put back in neutral and it dropped back down to 1900 rpm.  Rinse-lather-repeat.  

Messed around with it and found similar behavior when it cooled down (sub 150 degrees), but the idle would only jump about 200 rpm.  

Sometimes the idle would jump immediately upon putting it in gear.  Sometimes it'd take a few seconds.  The check engine light only came on after messing with it for awhile and that was when it was clearly getting a too hot.  Let it cool down a little and it never came back.

It is a bit of a schlep to the dealer, so that probably won't happen until next weekend...'thought I'd toss it out here and see if anyone may know what is lurking in this new scoot.

Thanks in advance.

Tim

 

 

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You should get a factory service manual, and stop guessing....

You are adjusting the idle the wrong way....you turn COUNTERCLOCKWISE  with the knob in the pushed in (normal) position, to raise the idle. Motor should be 2 min hot, and in neutral. Turn one click at a time till you get the idle you want. About 2000-2200. 

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You should get a factory service manual, and stop guessing....
You are adjusting the idle the wrong way....you turn COUNTERCLOCKWISE  with the knob in the pushed in (normal) position, to raise the idle. Motor should be 2 min hot, and in neutral. Turn one click at a time till you get the idle you want. About 2000-2200. 


I did. I misspoke. Never could get it to idle that high in neutral no matter where the knob was.

And still had idle jump a lot when putting in gear.

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6 minutes ago, Fogerson said:

 


I did. I misspoke. Never could get it to idle that high in neutral no matter where the knob was.

And still had idle jump a lot when putting in gear.

 

OK, so you need to do a passive reset of the ecu first.

Cold motor, NO THROTTE OR FAST IDLE KNOB, start the motor and let it idle. You must not use any throttle what so ever for the next 3+ min.

You want the water temp to get up to 190+ (left radiator too hot to touch) before shutting the bike off. Restart, and now the 'swing range' of the auto adjustment will be re-centered.

Ride the bike for a few minutes, then set the idle as needed.

If you cannot get it to start due to temp, you will have to wait till it warms up.....

If you still cannot get it to work, you have a damaged idle/fast idle plunger.

 

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Some good news, your procedure worked to get the idle @ 2000 rpm.  Some weirdness though...

About the time the bike reached 190ish (I have a radiator cap with a temp indicator), 5-6 minutes in when I was about to shut it off, the engine died.  I continued with the procedure and the idle was about at 1800 rpm, whereas yesterday, it was at 1300 rpm at that setting.  Got it up to 2000 rpm with a few clicks.

When I put it in gear, though, the idle still jumps from 2000 to 2400-2450 rpm.  And I noticed some lean pops as I'd let off the throttle (don't know how normal this is - new to the FI 4 stroke world).

 

Edited by Fogerson

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Yeah. Looks like we are dealer bound later in the week. I’ll let you know the culprit.

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