KX Riders
Maintenance & Technical => KX500 Original => Topic started by: jdv500 on November 08, 2004, 12:45:01 PM
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HELLO,
NEW TO THE SITE,41 YR OLD RIDER. Kx PROBLEM IS THIS; I'VE JUST BOUGHT A VERY CLEAN AND SEMI-FRESH 2001 KX500, AFTER ALL THE FLUIDS AND FILTER CHANGES, I PUT FRESH GAS AND OIL IN IT AND WENT FOR OUR FIRST RIDE.
** AFTER ALL RUNS OF ALL SPEEDS, I CLOSE THE THROTTLE AND COAST ALITTLE, BUT THE ENGINE SURGES AND BUCKS THE BIKE FORWARD 3 OR 4 SMALL TIMES, BEFORE IT WILL ACKNOWLEDGE THE SHUT GAS AND THEN IT WILL MELLOW OUT ON IT'S IDLE...
IT DOE'S IT REAL BAD IF I DO A HIGH SPEED RUN AND CHOP THE GAS ,(CLUTCH-OUT) AND COAST, THE BIKE SOUNDS AS IF I BLIPPED THE GAS REAL FAST 3 OR 4 TIMES, BUT I DON'T- IT DOE'S. AND. WHY IS THIS, PLS.??? NONE OF MY PAST BIKES HAVE EVER DONE THIS,, KX'S AND KTM'S...
THANKS, jdv, sorry for caps.
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Hi, welcome to the site, I will start by saying mine does the same. Just like you describe. I believe it is normal for the big KX due to vaccume. You might want to do a search on jetting, you will see that it is pretty normal and I've done ALOT of research in trying to rid the KX of surges and to get an idle.
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My new 04 500 does the same thing. The jetting thread and some others(surging) put my mind at ease. I thought for awhile my throttle was sticking. But no, it's just the big cylinder firing. Excess gas and the air vacuum I guess. Only does it after wide or near wide open blasts. The only bike I've owned that's done it too. My only big bore. :wink:
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jvd500,
Hope thats a "KX" problem (KY problems are kind of personal-HA HA). Yeah just as everyone has said that surging is normal. Mine probably does it worse than most but is not an issue when riding. Take it a a sign that your jetting is pretty close. Welcome to the site. Cam.
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I've had three 500's since i was 17 and i'm 36 now and so far and my 04'kx500 does it to , consistency is a good thing. The first (85)and last(04) make a almost knocking noise that i have learned to ignore, some do and some dont. I tore enginge and split case on " 04" at 4 hours and replaced rings,upper bearing and clips cause i was there and nothing was found abnormal anywhere.
eric 04kx500
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hey there,
after looking around within this great site i've learned alot.!! what to worry about and what not to worry about concerning my surging and run-on...
during the past week or so, i've went out and bought a new pipe, higher octane gas, diff main jets and pilot jets, and a new air filter. ** i have installed them all and will ride today. it's been really cold and wet and windy here in north alabama. but it looks as if today can and will be test day as it's cleared up greatly. , i'll write back afterwhile, joseph
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My 94 has done the same thing since day one. The best combination is having the jetting correct. If you can dial in the slow jet you should be able to remove "most" of the surges further by adjusting the air screw.
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My 04' KX5 dose the same too.
Must just be a KX5 thing!!!!
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Yep, my 90 does it also :)
Which can be a bit disconcerting for mates having a bash on it :wink:
Especially considering that mines set up for the road and in Supermoto trim.
Kind of revs up with a BRANG then off the juice with a TANG, Tang, before the revs come down.
A mate got off it and sait that he had much more respect for me as a rider getting it to go so fast and still between the hedges as it can lift a bit on WOT :D
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I'm a bit late replying but for what its worth my kx used to surge then I bought another carb off ebay (it was cheap) , since then the surging has stopped completely . the old carb was a pwk39 and the new one is a pj39 otherwise they have the same jetting .
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I tried a new carb too and it did help but not totally. Someone suggested that an airleak or bad slide could cause the surging.
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It all has to do with jetting. If the jetting is slightly rich down low, the surging will leave or clear up. But, running through two carbs and two KX500's here locally, it is pretty d**n normal. I did get ahold of a 41mm PWK carb from Pro-Flo and it is JUST the same after jetting the low-end to perfection. Nothing has changed even with a new carb, it is just as bad. Which does not bother me now, did though, like hell it did.
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hello, it's been 3 months since i posted this surging thing above. i've installed a ton of mods, maint parts and dress-up goodies on my 01. i'm very happy with it but even after the new top end and having the kips valve completely cleaned , mic'd and reinstalled, it still has the same ole' pulsing, right at the end of some hard throttle. i 've jetted, 54/165, response is instant. i see here within the site that roughly 9/10 owners have come to terms with this kind of issue.
**** if i had to make an educated guess at it; i'd say that it's the exhaust gases right out of the flange and the reverbing air flow in the chamber that are trying to get by each other, sending a false signal to the valve actuator in the process- via the last-in-line exhaust air just entering the valve........like an accordian/ ripple, this is just me............i've heard all the other hunches, is in ; case seal leak, carb slide worn, pilot jet too +/-, reed valves or boot cracked, valves out of timing... but even after we've cleared all these up, us and the some new 04 owners are saying the same thing. like you all have said above, we have learned to live with it or grown accustomed to it, i don't even think of it at all now adays when i ride, the bike has tons of great qualities to enjoy, but it did sound a bit odd to hear my bike as i was watching a home video of me on the bike.
thanks and enjoy...
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May be hard to compare the two but my 87 500 use to do the same thing. But after 1 size smaller main 1 size smaller pilot and lowering the needle jet one slot. my engine will just wine down to idle as the bike slows or if I roll off to a lower speed it runs fine. I changed the jetting just to clean up the throttle. When I first rode the bike before jetting I can just wine out 3rd and back down off the throttle the bike would surge and seem like it would surge forward. Have you lowered your needle jet :?: How is your idle speed set :?:I have my idle speed set as low as I can get away with. With the throttle rolled back to idle after a high speed run, I think the only air that is going to enter the engine will be under the slide and with the idle mixture screw. I think the only fuel the engine may get is going to be through the pilot jet. There may be a fine line here with the amount of air and fuel vers. piston speed. I think what I am trying to say is the slide hight(idle setting)and air mixture screw turns in or out ,after rolling off the throttle may let to much or not engough air to mix with the fixed amount fuel going through the pilot jet. Man it's getting late going on 1 a.m I hope some of this makes scents.
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thats sounds like good stuff there.
my idle is set just enough to keep it running barely, just as yours. my needle is 2nd clip from the top. i have to admit that the surging is alot less then when i first got the bike. and not really an issue now adays. even if it's still present. your right with what your saying there, i thought that with the slide down all the way, just a crack of day-light at the bottom to allow air to mix with the pilot jet then into the reeds. your thinking this may be the source of the problem.?
* up kinda late on a work night there huh.? thanks... joe
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If you think logically; the ONLY thing which can cause any engine to fire with a closed throttle is that the engine gets air/fuel mixture anyway. The engine cannot fire without the air/fuel mixture. I don?t have idle on my bike (don?t? want it) so my throttle does close shut.
When I tweak the air/fuel ratio really lean the engine is less likely to fire - but it still does. This can't be caused by any leaks; its malfunction in the carb or just poor design since we all experience it more or less (including me). If it?s a serial fault, I would like to know what it is. I am suffering from this when I have the motard kit on and riding on tarmac. It's not so bad when riding in slippery mud mainly because I don?t notice it then.
I switched carb last year to the PJ (same as orderofsion) and the problem went away. Unfortunately, the carb I bought was cr*p, so back to square one. I have recently bought two additional PWK-39's which I will tweak and see if I can fix this problem.
//John
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well, thats another one of our many therories, and yes, we'd all like to know what it is, the problem- cause of surging. thought his site tons of owners of all yr models are having this big or small. we all have our own hunch on what it may be / can be. case seals, worn slide, kips valve worn or out of time and of course jetting. well it seems that this will continue to live with us as long as we ride this model we've chosen. unless we all join and hire a team from nasa and hook probes all over it. we've learned to live with it, cause the goods far outweigh the bads with our 500's. logically. no worries. joseph
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John,
What is the basic difference between the PJ and the PWK carbs. In particular is the slide the same shape or lots different. I still feel the surge is caused by the PWK carb inability to hold back the big vacuum the KX makes. A different slide shape (PJ?) may be the answer. Cam.
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Cam,
Check out
http://www.sudco.com/Diagrams323728/exppwk.gif
for the PWK and
http://www.sudco.com/pj_diagram.html
for the PJ.
If I understand things correctly, the PJ is biased towards ATW whereas the PWK is purely motocross.
The major differences are; on the PJ, the idle is adjusted by twisting the choke knob rather than adjusting the throttle, and the throttle is oval (not flat-sided). I am way out of my league if I could claim to understand why this would change the behaviour of the KX500. I am a computer nerd with a mechanical background.
I am sorry if I offended anyone. I do realise that there is no silver-bullet magic solution for this problem and I am not saying that MY ideas about this are the correct ones. I am merely participating in a discussion and applying my limited logical thinking capacity. No fuel = no fire. The problem might be related to the distance between the reeds and the piston? Or an inherited design flaw in the intake manifold ? really, I haven?t got a clue. My goal is to fix the symptoms and I aim to give it a go.
//John
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I seem to remember reading that one way to give more power to a CR500 (which already have a PJ carb) was to use a PWK39 carb so would have thought that using a PJ would have been a backward step :?
Not used one so I am a bit in the dark about that.
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john ,
no problem, i've seen within this site that there are 1 or 2 guys that have never even heard of this run-on surging thing in their 500's, nor did they know what the fuss was about. we love this bike and for me, i'll keep it forever or even get another to add to my arsenal.
earlier, you said that you prefer no idle,, i think that i know why this is,you use it for engine braking/decel.? also you said that you ride the 5 on tarmac.. where and when do's the surging happen out there, if ever.?, jdv
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Jdv,
Same problem there - after full throttle a hard brake. With the grip on tarmac it is more noticeable; as in using the clutch not to loose the optimal track.
I am used to it but my friends are not. They usually just try my bike once.
//John
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John,
Yea I could believe that on tarmac the surge would be a bit of a bother, especially if you were leaned way over (dragging a knee?) decelerating into a corner. Maybe a good reason to try a PJ. I had one on an '87 CR500. It worked very well with a similar engine and intake to the KX. Cam.
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I am used to it but my friends are not. They usually just try my bike once.
//John
Aye, mine does it and the mate that I have let ride it hates the couple of Brang Tangs it gives out :lol:
I Ride mine on Tarmac but prefer it to idle as it pisses me off having to blip the throttle in trafic (especially if there is a police car about as they give the bike FAR too much attention as it is) cos it's a bit too loud.
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Oki guys, I maybe have the solutions for the problem! : :wink:
This is my teory: :idea:
I think this is a KIPS problem. :shock: :shock:
Every KX-cylinder I have tuned they all (1989-2004) have a problem with KIPS.
Either with opening or closing or both.
The opening it?s no problem with shims and new parts, but the closing.....
I have found out that KIPS is OVER-closed because of to short stopbolt(92066)
for the rod(49046) who is moving the KIPS.
When the rod moves too far back at low rpm, it?s opening the sub exhaustports
and let some "new" fresh air/fuel in exhaustchamber and it
ignite there,it?s VERY warm exhausts(600*) there.
I have no problem with surges/pulses, I always"take care"
of this KIPS problem.I put in a old steel bearingball and shims(92065) the stopbolt(92066) to right distance. :wink:
You have to take away your pipe and SEE (use flashlight) inside exhaustport how much distance you have to adjust.
And one more benifit it`s more lowend power because of right porttimes when the sub exhaustports isn`t engage at wrong time :twisted:
IF you think I`m right here and you ALL people fix your problems with surges/pulses ,please send a little money($$) to PAUL(admin) so he can afford to
have this site still going! :wink:
(you can read about this in old post)
//doordie
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Doordie,
Thanks Doordie, I'll test out your theory on my bike. It surges worse than most and is due for a rebuild any day. I'll check out the KIPS timing and see how far off it is. Will be easy to tell the difference when I fire it up for break in. Cam.
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KXcam22,
I belive this take care of the most of problem! :wink:
But do we have a good "electric man" who can
check more precise if our engines fires 2 times
each stroke? :roll:
Why I think that?
I have buyed a TINY-TACH and it show double RPM.
It suppose to read 1 spark each revolution and now
show twice..... :shock:
If it fires twice every revolution, my teory of the surges and pulses
come to MORE sense! :lol:
(I will explain later)
//doordie
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KXcam22,
I belive this take care of the most of problem! :wink:
But do we have a good "electric man" who can
check more precise if our engines fires 2 times
each stroke? :roll:
Why I think that?
I have buyed a TINY-TACH and it show double RPM.
It suppose to read 1 spark each revolution and now
show twice..... :shock:
If it fires twice every revolution, my teory of the surges and pulses
come to MORE sense! :lol:
(I will explain later)
//doordie
Are you sure that you have the Tiny tach wire wrapped around the HT lead the right number of times? aparently if it's wrapped round too many times it can give a false reading.
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Doordie,
I'll put my new super oscilloscope on my ignition and see. Is it possible your tach is seeing the coil discharge and then charge again. Also in your KIPS theory how would jetting fit in? Seems that for most the surge only shows up once the jetting has been leaned out. It's completely melted here, ice is rotten.....and then it snowed 14". Cam.
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demographic,
I wrap it 4 times as instruction describe.....I will test fewer wraps.
But I borowed a another tach(2 stroke)with crocodile jaw from a friend and
it shows the same double rpm,very strange. :?
KXcam22,
Thx mate, try your oscilloscope and see if you can figured out it. 8)
By the teory, maybe with leaner jetting you get more fireable
air/fuel/old exhaust mixratio inside exhaust chamber,but I will "think" some more
and see if I get some another clue. :wink:
mun,my finnish friend,do you have a clue?
But IF we have twinsparker here, It?s a solved problem! :wink:
Adjust your KIPS anyway guys and feel a right adjusted engine with
a huge grunt of lowend! :lol:
The weather is F....ed?up here too :evil:
one day cold ,next day spring with plus degrees. :cry:
//doordie
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Some finnish "electric man" told me once that KX500 fires two times every stroke!
I have MyChron Light MCR (http://www.aim-sportline.com/KART/light.htm#MCR) on my old -86 KX and it can be configurate "rmpratio". This rpmratio is on my bike 2 = two fires / stroke! I checked this just in garage.
I have always setting my crossbike no idle. I can't ride with idle, horrible.
No problem when shut off throttle, with stock Mikuni VM40 and now VM44. Over 20 years ago 2-3cm of cylinder basegasket blow off my -82 CR480 and it run then 2000-3000rpm "idle".
sorry again my awful english :oops:
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mun,
No problem with your english,we understand the most BUT don?t spell
in Finnish plz! :lol:
(I spell as crap too)
You have a lot of experience you can share,I promise. :wink:
But the teory,I can be right here? :?
If it fire twice/stroke it will explain a lot.
Maybe a BIG fire and then a smal clean-up fire 20 degrees or something later?
Kxcam22 is testing too,see what he comes up with.
//doordie
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Doordie,
Thanks for chiming in! Seems like you could be on to something - two things actually. The second spark would be controlled by the CDI rather than the rotor and stator..? If this is the case, it might / could be verified by someone with a different CDI like aftermarket stuff? It seems like the 250 has a feature called "twin spark" which is provided by the CDI (could this be the same?). Google it to see some info.
Mun,
Don't worry about the language, everyone understands what you mean - Ykkeskanava. :wink:
//John
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John,
Yes,it?s controlled by CDI if this is true.Maybe enough of power to get
a little spark after the main spark some degrees later. :wink:
Did article told what year of KX250 this twinspark CDI were on?
Hope KXcam22 or someone could with right "stuff" solve it. 8)
//doordie
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Doordie,
It seems they existed on the 2000 models at least. It might be that it's the same stuff all over but they started to market this a feature Y2K? I really don't know...
//John
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I have a PVL system on my KX500, which is a inner rotating flywheel, totally diffrent stator, all new CDI, Coil, ect. ect. Totally diffrent ignition...
EDIT: Oh yeah, same issue. :roll: