KX Riders
Maintenance & Technical => KX500 Original => Topic started by: John on September 08, 2003, 11:26:31 AM
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Hi all,
Problem for discussion:
After I have revved the engine a lot and let go of the gas I get these nasty kick-backs from these single massive 500cc explosions. As opposed to what could be called two-stroke engine break..?
Cause?
I suspect this is caused by the fact that the engine is suffocating, i.e. not getting enough fuel. Baring in mind that this is low revs, I figure the problem is caused by either the pilot jet or the air-screw or something I have totally missed out?
Solution:
I?ve tried to re-jet the pilot jet to 64 (latest). I have changed the float level (pisses fuel even when tilted 10%), changed the reed-valve. Almost everything except changing the carburetor itself. The only result so far is a total lack of idle and - the kick-backs persist. I have not tinkered with the ignition timings or spark-plugs. The bike always starts and behaves in all aspects except this one.
This is really starting to annoy me :evil: When it happens, it kind of pushes me out from the ideal line in the slower curves (more so on tarmac than on gravel). I am using the clutch as a workaround to cut out this effect.
I know others in this forum have similar experiences on their KX-5's BUT does anyone have the solution :?:
/John
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Hey John, those kick-backs are a sign of loading up. The 64 p/j is a big pilot. What happens if you jet it with say a 58?
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Paul,
Yes, been there done that... with a 58 pilot jet the bike idles and the kick backs are more frequent (if it makes sense?). I have changed the jetting up and down but I get the best result when it's rich. The drawback is no idle but what the hell, who needs idle anyway?
It approved somewhat after a top-end overhaul I did recently. The previous owner had two top head gaskets. I just have one of the new slim ones = higher compression ratio.
Question!
Am I the only one who is experiencing this? I talked to another KX-5 rider here in the UK and he had the same problem. Please tell me that there are more of you out there who have the same KX-5 behavior as I do. I do want it to be a KX-5 problem rather than a ?John? problem?
/John
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Did you have the bottom end pressure tested when the topend was done? If not look behind the flywheel and see if there is any sepage from the seal. Sounds like you maybe sucking air in from the dry side seal and causing a lean condition. This would explain the need for the big p/j and the surging.
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Paul,
Thanks, nice one! I'll check it out tomorrow in the daylight.
Cheers,
/John
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Hope thats it, if not we'll work on it some more.
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Hi John
Did you ever solve the kick-back problems? I having them too you see and it really feels like the bike will low-side in every corner when the kick-back comes.
Is it because it's running too lean or does it have a leak?
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SuperMotoKX,
I haven't had the time to thoroughly investigate what the cause of the problem is. I checked out the engine and there is no obvious sign of leaks. But the plan is to break the engine this winter - if I have the time... The thing is, I am kind of busy. Wife, kids work and what not? I just wish I was single sometimes and could use all my spare time to do whatever I want to do.
/John
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Are we the only two kx5 riders in this forum that are having these problems? Anyone else?
I talked to a Kawa mechanic today and he suggested the ignition timing. But in the end I guess I gotta do what you do: Complete engine service this winther - bugger.
Martin
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Yes, I have been thinking about the ignition. I figure it's either an ignition or carburetor related problem. I have checked the top-end. Could it be inherited by design? But I guess more people should have the same problem?
Checked the engine outside for leaks and the tranny for compression but I don't think it leaks. I am reluctant to break the engine. If I don't have to - I wont.
I have tweaked the timing some (not really much) - no change. Maybe a different spark plug? Haven't done that yet.
Well, I know there are others who have the same problem. Talked to a Kawasaki mechanic who rides a 500 motard. He's got the same problem - but he doesn't care. He said it is inherited by the big stoke. He was actually the guy who told me that the engine doesn't get enough fuel. Tried with the choke on and the problem disappears - but then aging - that doesn't prove much does it?
/John
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Proves there is a lean condition somewhere. Is the carburetor boot old and cracked? Is the needle as lean as it gets? I'm tossing things out now that effect air / fuel. Something has that bike running lean. All we have to do is figure out what it is...
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Maybe.
If I choke the engine - it dies on low rews. A dead engine wouldn?t give you kick-backs...
Been through the carburetor and everything so many times now and I am pretty sure there is no leaks. Got a new V-Force reed cage (and a spacer) as well. All in good conditions including the boot, new stuff but old carburetor.
The needle (if you mean the throttle needle) shouldn't have anything to do with this problem? The throttle is not open when this happens. Would only be air-screw and pilot jet.
/John
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Well now, you never mentioned it was dead when the choke was on :lol: Yank sarcasm, nothing to worry about :D
Umm, well lets see here... It only does it when the throttle is let off correct? So the only places it will get air are from between the carb and the jug and from the dryside engine seal.
So logically there are only a couple of things here, a reed cage gasket, a carb boot, and a seal.
Its a very long stretch but is there any ooze around the base of the spark plug?
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So let me get this straight: The kick-backs disappear when you ride with the choke on :shock: ?? Well I've got to try that.
What's your carb setup? And what oil-mix ratio are you running?
I'm also racing this bike as a motard (the 250/500) and the kick backs are a pain :cry: , I'm inches away from crashing everytime I go into a corner. It seems to happen more often when I gear down hard and the engine revs high without opening the throttle. Does that make sense?
I've been fiddling with varius sparkplugs and I think a NRK 9 helps a bit. But the bike just runs better with the 8.
I've also tried revving the engine before going into turns, but a) It screws up my braking and b) I'm not sure it works at all :roll:
Oh wait...Could it really be the carb boot? Mine is not too good and to be honest - the carb doesn't fit 100% correct in it, because the 250 tank is in the way. I'm getting that sorted though as I'm making a smaller alu tank. But could that be my problem?
Martin
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Nah...
I am quite convinced that everything is more or less OK. Sucking in air was the first thing I checked and I don?t think it does. New gaskets, new reed cage.
This is an 89er. Could this be a problem related to this year?
Scary the bike is actually older than my oldest kid! When I think about an 89er I still think it's kind of new. I guess I'm stuck in my teens where 89 would be a quite new bike!
I really appreciate all your effort here even though it might not sound like it. It could be the famous language barrier?
/John
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:lol: It doesn't bother me, I just can't imagine why that bike is doing that if everythings good.
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Well I think there are more out there who is experiencing the same problem. Could it be that this problem becomes more obvious when you ride the bike on tarmac (blacktop for you guys in the US)? I mean all of us so far are motarders.
/John
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Solved!
Having discussed this problem with a serously good mechanic he helped me to draw to correct solution - which I have verified. It's so simple when you think of it. :oops:
Problem; throttle not open but the engine still delivers power. It sucks air + fuel even though the throttle is closed = worn throttle! That's what you get for buying an old machine...
Bought a better second hand carburetor and the problem is gone. The new carb is Keihin PJ not the PWK which is the original for KX5. This carb is more biased towards off-road not MX. A bit too slippery outside today to verify all aspects of the mod but it seems to be OK.
The PJ throttle is oval not flat. And there are different models / sizes of throttles for different setups / bikes. I am not sure I can ever get this carb to work well with my bike unless I buy all sorts of throttles and needles and keep on testing. This will probably cost me more than a brand new PWK carb...
I will keep on looking for a newer PWK carb and see if that solves the problem.
/John
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Hello everyone!
You talk about kickbacks and i have had them to,only solution is a new carburator or fix the old one with new aluminum in the slide.Someone talk about buy a new carb... but i have somes friends here in Sweden who prefer LECTRON-carbs.. 38mm-48mm. They were very easy to "fix" to right jetting `cause only a a needlejet and a powerjet.They are is easy to reech to.We have a company here in Sweden who sells them(EBOS high performance), but they are from US,so it must be easy to get them for you,hehe.
Cost about 450-500$ (5000kr)here.I have not try one my self ,but i will....!
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The mechanic - Bengt from http://www.deltamc.se yet another Swede told me that the newer PWK cabs has a crome throttle and is less likely to wear out. I will se if I can find one of those before I buy a new bike...
/John (Sweden rules!)
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Mine is a 94 and I have the same problem. What I noticed is that it's worse now that I put on the carb spacer and flywheel wieght. It makes me think that mine is related to a leak. Nothing else changed...
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Just a thought when you mention the cage and spacer. When you cut the intake boot down, did you nick the small factory "bead"seal on it? It would be a very easy place to develop a small intake leak. Even more so with V-Forces recommended "hack saw blade" method of cutting it down.
Personally, I didn't like the very little narrow factory seal on the boot and opted for an additional gasket at that point for a total of three gaskets at the reed spacer, cage and boot connection. Anyone else notice this same thing at the boot seal area?
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look like a leaking needle seat and too mush advence on timing!!!!take a look at the back plate if not loose by vibration or (hot point) in combustion chamber!!!! engine pingking????
sorry for my bad english!!!! :oops:
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When you cut the intake boot down
I didn't cut anything...what was I supposed to cut??? I did use the provided Moose gasket between the boot and the spacer and another between the spacer and the jug.
When I had it apart I went thru the carb. I noticed that needle jet button still had spring but would not hold the floats up. Is this normal.
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I"m not sure if the springs still intact how it wont hold the float up?Is your float level set right?I found mine worked best set a little higher than listed in manual and cleared up a rich condition I couldn't get rid of with jetting.Does your carb overflow with the bike only leaned over slightly?If in doubt it's not a bad idea to replace the float needle and set your float level,try it on the high side of specifications.
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Banshee srb,we may not all have the English language in common,but whats good is we all have fun riding in common.Thats whats important,so dont worry about your English,we can read your writing just fine.
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i had that problem the needle had a litle ridge and i was suspecting a leak from the float so i change both and i had a little to much advence on timing so i retard it i set the back plate in the midle just like they say in the manual shop and i solve the proble!!!! :D
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I didn't cut anything...what was I supposed to cut??? I did use the provided Moose gasket between the boot and the spacer and another between the spacer and the jug.
When I first made the post, I didn't see the original post went to two pages.
The cutting of the boot was for the V-Force cage to fit, not for the install of the spacer. Sorry for the confusion.
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Oh ok! I was scared for minute.!!!
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Running into the same problem on my kx. Problem has gotten considerable worse after installing the moose reed spacer (gaskets?) and Steahly weight. Any further suggestions. Could float level cause this?
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I experienced what I think is the same problem on my 90, when I let off the gas it would pop and there was a power surge, bad enough that the bike would buck pretty hard. In my case this was caused by a rich condition in the carb's idle/ slow circuit. I changed the slow jet from stock to a leaner jet, I can't remember exatly what size though, this completely cured my problem. Might be worth a try. Good luck.
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I personally will try anything to make this condition go away. It's annoying as hell.
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kawdude,
I wish I could remember what jet size I ended up with (been over a year), but I think it was a 52 or even a 50. I went through several progressively smaller jets, and the problem kept getting better, and it finally went away with just the jetting change. Hope this helps.
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That's ok. Mine currently has a 162 main with a 62 pilot with the clip on the top notch so something definately isn't right. I personally think that it's very rich. Has no go past mid throttle and lots of splooge.
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Ialso had to drop my main jet several steps to get my plug reading correctly. This helped a lot with power and with the splooge.
As far as lacking power above mid throttle, have you checked your KIPS valves to make sure they are timed, and/ or not sticking?
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good point paul on kips valve.put the cover and drop pipe and a light open and close valve by hand noticing position of cut out of the drums as well as the movement of the exhaust flap.stay small on the pilot jet,noticing idle and watch oil mixture.i personally don't like the bel-ray.seen a lot of gummed up systems.this is to say the rest of the top end is in good shape.
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Kawdude,
A simple test; adjust the idle screw all the way out so the bike does not idle - at all. If you then ride the bike and it still bucks you have a carburetor problem as in worn out throttle.
The engine should not get any air/petrol mix ergo should not be able to ignite.
//John
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Good points. One thing I notice that may or may not be related is that the needle on the slide moves up and down within the slide. Not a lot but enough for me to say that has to effect something.
Kips valves seem to be in good shape (surprisingly). How far does or should the lever from the lower case move? With the jug off I see that a lot of movement is needed to open the side valves and raise the center because of play in the KIPS gears.
Currently the idle screw is all the way in and the bike "kinda" idles. I will adjust it and see what happens.
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Kawdude,
With regards to the carburetor, the needle doesn't have anything to do with the lower rews but it does affects lower-mid / mid-high (you might call that middle rews?).
I had the very same symptoms as you did until I changed the carburetor. Tried it all, tweaked the timing searched for leaks etc. but fact remains, the engine does not ignite unless it's got air/fuel...
Changing the idle jets to really small ones will also work. No fuel - no kick-backs...
If you dismount the carburetor and check the throttle-play when the throttle is mounted you will probably find it is not a perfect fit... That?s causing your problem. It sure caused mine.
I do agree, it's very frustrating when the bike almost throws you off the road just because you do not rew it.
//John
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I'll certainly check what you suggest. I think it's odd that the idle screw is all the way in now and it barely idles. That along with the needle bouncing up and has got to cause a problem somewhere. I agree that the needle does not come into play until mid but should the needle move up and down in the slide. Thoughts on what this sloppiness would do.