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Discussion Starter #1
hello,
i'm a 41 yr old rider, this is my 1st 2001 kx500. while riding it and at any and all gas settings and rpm's, the bike will lurch forward and surge 3/4 times before it will begin to decell. this is with the throttle shut and clutch out. the bike wants to roll on and surge a few times before it will idle down. it will only act normal if i pull in the clutch right after the run while the gas is shut, but then too is some bucking and surging also.
** after a straightaway run, i close the throttle and roll, with the gas off the bike will sound as if i've blipped the gas 3 times real fast, but i did'nt.!!!!!!!!

every other bike i've owned and ridden behaves normal after a hard run and shuts down to idle almost immediately, what gives with my kx500, i want to get this right so that i can enjoy to ride it, rather then worry about it. thanks for any help here guys, joseph
 

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AZ's Official Mechanic
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sounds like its going lean on ya when ya shut the throttle. try doing it SLOWLY and see if it does it. if it doesnt then i would say you need to play with your mixture screw on the side of the carb and richen it up a bit (more fuel) its actually really bad to just snap the throttle closed on 2-strokes since you end up starving the whole motor of gas/OIL
what elevation etc are you at ? what riding conditions etc. ? more info
 

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Discussion Starter #3
more on kx500 surge and pulsing......

thanks for the reply ,,,
my mixture screw is at 2 turns out as the maint book states, i'm here in huntsville, alabama, 68 degrees temp, don't know my elevation. i've riden and own several 2-stroke, shuting the gas to enter a corner or for any reson you find yourself off the gas, i've done this all my life and never had (this) happen to me, i'm wondering if it's a kips valve, (kx only trait or do i need to do some tuning to get rid of this., thanks again, more soon. joseph
** shutting the throttle during recel is a normal event, i'm having throttle run on, that is bugging me bad, need it gone.
 

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Discussion Starter #4
oh wait,,,

starving the whole motor of gas and oil you said.???
nah,,, not the whole motor, but the top end, only.... And then you have the pilot jet to take charge as you enter into an idle running condition.
atomized fuel and oil are a constant/ ongoing process here, no worries there, or here...thanks, joseph...
\
you asked of what type of conditons i'm running, well, just a few flat ground speed runs to gauge the response of the bike as it's new to me.. got up to 4th and touched 5th gear then backed off the gas and let it roll out... but it's feeling and sounding like it's bucking and revving still while closed....
it's impossible to hurt a 2-stroke eng, while rolling will the gas off.!! why.?? all the constants are still working fine, lube is flowing, air/oil is misting, combustion chamber gets a break from the heat, hummmmm. but thanks, there.
 

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ya i realize all the things you say about 2-strokes. ive ridden them all my life also.
but i think you still lean esp. since its cooler now. maybe wrong plug heat range ? make sure you carb slide is working smoothly. have you done any carb work lately ?
 

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Sounds like you have a left side ( sitting on bike) crank seal sucking air or an air leak via the crankcase, which would obviously cause it to run lean and quite hot.
 

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you just answered your own question with your last response.
if you are revving the bike hard and shut the throttle its not at IDLE instantly so its only getting that small amount of oil/gas that the pilot can supply NOT WHAT THE MAIN CAN SUPPLY at WFO. im not gonna lie and say ive seen anything bad happen by doing this but the mech. that told me this has been doing bike mech. work for over 30yrs now. just an FYI :wink:
 

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Discussion Starter #8
answered my own question.??

i've own and rode many 2 strokes, thius is the very 1st to have a bucking and surging problem. all my other bikes as well as the kx sites veterans tell me NOW, that this is a kx500 specific problem and that it inherent in the kips exhaust valve design and OLD and NEW 500's have had or are having the very same problem. all have experimented with the main and pilot jets, fuel/ oil ratio's and a wide variety of plugs, they said and i have since tested that you can reduce the bucking/surging somewhat, but not rid it from the engine completely.

now, in my saying that i shut the throttle after a full run at slow or high speed is'nt answering my own question, it's a riding trait that we all do for whatever reason, please feel free to slam your gas shut to up a turn or just avoid a disaster, (((The pilot and main jet overlap in their jobs))), as far as the misting in regard to where the throttle is at and the demand of the vacuum from the intake....!! your friend the 30 yr guy.??? remember.? he told you that slamming the gas off is bad.? 2 srtokes infrom even in the early days have had to factor in abrupt throttle decel and various trailing gas too, it's all good my friend...hummm. i'm a 19 yr aircraft mechanic just back from iraq, we do tons of turbine eng work over there too, and slamming the gas shut on the t-701c turbines is a normal occurance. really, a 30 yr guy.??? more when i can, joseph
 

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hey fellow 500 owner,question #1.is the bike low hours or have a fresh top end? if so the compression is at an all time high.this alone creates massive suction in the crankcase which will cause the surge you talk about.check the crankcase vent hose to make sure it's clear.
now, the big issue.if the bike is stock jetting wise it's all wrong. the big kx comes stock jetted very rich.they are known for fouling plugs. have you seen this with your bike? I have a very good jetting chart I can email you if you want. I have seen this surge problem with every kx500 I have owned.Im on my third.jetting it right and getting it broken in will make the problem all but go away.as i stated before,crankcase suction on throttle close will pull large amounts of fuel through the pilot and main,(if the needle is set to high) remember,there is a piston in there the size of a one pound coffe can.when you snap the throttle shut the motor becomes a huge suction pump.
 

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Scary Harry said:
It would certainly appear to be non-productive to ask a question and then to argue with those that answer. If you do not like the answer just ignore it and make up your own mind.
Perhaps a two stroke and a jet engine are two different types of engines.
I agree with Scary Harry. Now look for a airleak
 
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