extremely high rev sometimes???

[Nairns_Two_50K]

My 1996 kx 250 has an extremly high rev sometimes when starting from a cold. It happens mainly starting after trailering or after sitting for a period of time.  I have asked the dealer and nobody seems to know.  The bike will rev to the moon for maybe 5 seconds or so and then will fall to the high idle choke.  This is not just a high idle from choke. This is a super high rev that appears to be uncontrolable for under 10 secs.  My throttle is also not sticking. Throttle and slide are funtioning perfectly. Also the bike revs way up when running out of gas. Has anyone ever delt with this?

[stevea100m]

my 03 125 and 03 250 both do this and i never really figured it out. Ive taken both carbs apart and cleaned them had the floats checked and nothin so i just make a habit of hittin the kill switch to control the rev untill it idles down

[Nairns_Two_50K]

my 03 125 and 03 250 both do this and i never really figured it out. Ive taken both carbs apart and cleaned them had the floats checked and nothin so i just make a habit of hittin the kill switch to control the rev untill it idles down

  Somebody has to have an answer for us.  I do the same thing with the kill switch.  There has to be a reason for this spuratic start.  After it does it once at the beginning of the day it will most likely not do it again.  Not every time it does this but I have noticed after trailering it seems to be more prone to act out. It may just be a coincendence though.  Anybody else?

[Openclass]

My 03 250 does this too, same yours when cold and coming out of the shed after a little rest (Storage).

[agraebner]

First thing that comes to mind here is possible crankshaft seal leaking.  I had a bike did this till i replaced the stator side seal.  I guess it just leaked a little till it got running for a few minutes or it pulled a vacuum on the stator area.  The leak of unmetered air added to the rich condition of the choke = high idle

[Motorrad]

Sticky needle and seat....   replace em...

and do a leakdown test..

[DFL BIG BORE]

my k5 does always does this too! before and after rebuilding it,i drain carb when done riding and drain tank(i use c12).when its time to ride fill it up ,turn on gas lean over for 5 seconds,kick it over and rpm go sky hi,kill it,fire it right back up. then fine all weekend.only when sitting dry for a few weeks.bouncing around on a trailer gas has spilled out of the float,kinda like running out of gas the rpms go insane. mabey check your vent hoses,and gas cap vent.mabey a slight "air lock"on your gas tank

[elmo]

1, turn petrol off leav bike running, Does it rev high before the petty runs low?
2, Remove pipe for petrol from carb leave bike running, Does it rev high before dying?

Yes to 2 is normal, yes to 1 means at some point your bike is sucking air into the carb from somewhere... Lol not that that helps much!

[don46]

I have a bike that does the same thing, and I do know how to fix it but I'm to lazy to do it. So, heres the problem, your too rich on the needle and maybe pilot as well and to get it to idle you turn in the idle screw, to get it to idle creating a larger opening between the slide and body. As we all no colder temps create a leaner condition so when you start it it is a bit on the leaner side and your putting more air in causing more revs, once warmer you get back to the richer condition and it idles fine. Other than your bike running a bit rich, and you don't let it rev to the moon using the kill switch to keep it from revving to high you really don't have a huge problem. Most Kawasakis are jetted to rich from the factory, especially the needle, it is not un common to drop 3-4 needle sizes on a 250 as well as main and pilot. Jetting is an art and does take time to get right, what works for me won't necessarily work for someone else, remember temperature and humidity play a big part in jetting. At the race track it is amazing how many bikes you see that aren't jetted properly, 250's are the most common because they run well even if jetted wrong, 125's on the other hand have to be jetted right to be competitive on a pro level.

so there you have my .02 on the issue.

[hughes]

I agree with don46 on this one. I need to address this on my YZ250 as it does the same thing.

[Nairns_Two_50K]

Thanks for the input. That does make sense.

[Openclass]

Question: Will this jetting problem also lead to drolling or that black unburnt gas being spit out the rear of the exhaust?

I race and ride mostly Harescrambles. It was just my thinking that this was from not being able to rev (clean it out) most of the time.

[don46]

Question: Will this jetting problem also lead to drolling or that black unburnt gas being spit out the rear of the exhaust?

I race and ride mostly Harescrambles. It was just my thinking that this was from not being able to rev (clean it out) most of the time.

This is a difficult question to answer, obviously a well jetted engine should minimize the drool. the type of oil you burn has an impact as well. i would say that a quality synthetic gives you the best opportunity rid your self of drool. When we raced indoors we ran a synthetic oil that was smokeless made by redline, (these guys make great stuff, if your serious abour racing try the gear saver, the yellow not the blue, great stuff). My son rides our 250 2t and it never drools, my wife can get on it and make it slobber like a saint bernard, so even jetting isn't the whole answer.