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2012 KX250f Idle stays high after revving

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Hey guys I have a problem with my idle after I rev the bike. When I start it, it idles fine, but as soon as you give it a bit of revs the idle stays high and takes quite a while to drop back down. Sometimes it won't drop down till I let the clutch out.

Any ideas where to start looking?

The bikes done 30hrs and has just had the valves shimmed. The problem was there before the bike was shimmed.

Also I'm not sure if this is related, but when the bikes hot it gets real hard to start, and when I finally get it started it coughs and splutters for a few seconds before it comes good.

Any advice would be greatly appreciated thanks. I'm new to bike mechanics so you might have to dumb down some technical terms.

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Could be an air leak at the intake manifold or a faulty sensor like the TPS

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Running my second heat cycle the revs only stayed up for a half second. The problem seems to be fixing itself. It could be because my bike hasn't been ran in so long!

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Nevermind, the problem is back! The only way for me to get the idle to drop down is to turn the idle screw way down!

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Could be an air leak at the intake manifold or a faulty sensor like the TPS

 

Shawn, I know this is an older thread, but I know what walker is talking about.  Any ideas here?  Hanging idle on an FI bike . . . any ideas?

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Hmmm. Could it be the hot start or whatever they are calling it ? you know when you turn those it changes the idle. possible leak or something ?? sorry I sound retarded, have the flu.....

Al

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Hmmm. Could it be the hot start or whatever they are calling it ? you know when you turn those it changes the idle. possible leak or something ?? sorry I sound retarded, have the flu.....

Al

 

You may be on to something there.  It is a high-idle knob, but it looks just like a hot start plunger.  It is also subject to obvious wear.  Good post and hope you feel better  👍

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Shawn, I know this is an older thread, but I know what walker is talking about.  Any ideas here?  Hanging idle on an FI bike . . . any ideas?

 

Sorry not sure only had my FI bike for 12 months now and not experienced these issues.  

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yea you can set the idle low. These kawi like the running a tad on the high side. Also depends on where your riding. When i went to mammoth at 8,000ft i had to turn out idle up 6-8 turns. My sons bike actually got a slight bog because of it until we turn it up and ran the white coupler

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I got a 2012 used one and have the same problem, it's bloody dangerous to ride it like that. My mechanic said could be a leak in the intake system somewhere. Will be checking that next week but any more suggestions?

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Hey Indian, go to this link https://thumpertalk.com/topic/1085690-2014-kx250f-weird-idle-questions/

 

Then scroll down to my post and watch the video I posted. Go to the 11.54 mark and listen to how that bike Idles and tell me if that is what your bike is doing. I have a 2014 and it has done that sense it was new(5.5 hours on it now). This seems to be limited to the 2012 and up which have the dual injector setup. 

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Have you tried lowering the idle a bit. I'm going to try this on mine to see what it does but, it really doesn't bother me that much at all really. It doesn't seem to affect my riding.

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Hey Indian, go to this link https://thumpertalk.com/topic/1085690-2014-kx250f-weird-idle-questions/

 

Then scroll down to my post and watch the video I posted. Go to the 11.54 mark and listen to how that bike Idles and tell me if that is what your bike is doing. I have a 2014 and it has done that sense it was new(5.5 hours on it now). This seems to be limited to the 2012 and up which have the dual injector setup. 

 

I have an 11 with a dual injector set up (which means a 12 ECU) and I am having the same freaking problem.  Just random high idle when hot.  If I turn the idle down to normal when hot, it will stall when cold.  I checked the gear position sensor and it was perfect.  TPS is perfectly calibrated.  Two intake air pressure sensors have been tried, with no difference.  I have not checked the water temp sensor or air temp sensor, either of which could cause idle weirdness, but I bet they are fine. Nevertheless, I will check them, though it is a PITA.   Valves are new shimmed and seats are cut.  No valve leaks.  Compression is in the sweet spot.  

 

My gut tells me it might be the plunger itself on the idle circuit.  Mine is visibly worn.  Not by much, but it wouldn't take much for variable air infiltration, which would mess with the idle, just as a worn hot-start plunger could mess with carbureted bike.  It's a theory, but I may just replace the thing to see if that solves the problem.

 

If anyone else has a known solution, this seems to be becoming an issue with this FI bike.   

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I honestly wouldnt worry about it. Its not going to cause you to go wildly off the track at moments notice. I think it is just something kawai do. I run mine high anyway and i doesnt bother me a bit. You could always send team green an email or kawasaki in california and see what they say.

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Ok maybe I'm not comfortable as I've only ridden this bike once. And as all other bikes I would expect the revs to to return to normal when I shut the gas; it's quite a weird feeling when you want to coast in to a corner and the bike is still applying gas.

The scary situation is on jumps; I don't know what will happen as I've only done small jumps so far on this bike.

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Hey Indian, go to this link https://thumpertalk.com/topic/1085690-2014-kx250f-weird-idle-questions/

 

Then scroll down to my post and watch the video I posted. Go to the 11.54 mark and listen to how that bike Idles and tell me if that is what your bike is doing. I have a 2014 and it has done that sense it was new(5.5 hours on it now). This seems to be limited to the 2012 and up which have the dual injector setup. 

Well the only time I rode it I did something stupid; I turned the idle high to see if that cures it. I'll try setting it low again :goofy:

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