Author Topic: Kick-backs for dicussion... (Read 12394 times)

John · « **on:** September 08, 2003, 11:26:31 AM »

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

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

Paul · « **Reply #1 on:** September 10, 2003, 08:43:06 AM »

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?

John · « **Reply #2 on:** September 10, 2003, 08:55:53 AM »

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

Paul · « **Reply #3 on:** September 10, 2003, 09:04:05 AM »

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.

John · « **Reply #4 on:** September 10, 2003, 09:07:56 AM »

Paul,

Thanks, nice one! I'll check it out tomorrow in the daylight.

Cheers,

/John

Paul · « **Reply #5 on:** September 10, 2003, 09:09:05 AM »

Hope thats it, if not we'll work on it some more.

supermotokx · « **Reply #6 on:** September 27, 2003, 07:08:24 PM »

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?

John · « **Reply #7 on:** September 28, 2003, 08:27:02 AM »

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

supermotokx · « **Reply #8 on:** October 02, 2003, 11:26:55 PM »

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

John · « **Reply #9 on:** October 03, 2003, 12:27:05 AM »

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

Paul · « **Reply #10 on:** October 03, 2003, 01:43:10 AM »

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...

John · « **Reply #11 on:** October 03, 2003, 04:50:18 AM »

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

Paul · « **Reply #12 on:** October 03, 2003, 05:07:18 AM »

Well now, you never mentioned it was dead when the choke was on

Yank sarcasm, nothing to worry about

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?

supermotokx · « **Reply #13 on:** October 03, 2003, 07:01:46 AM »

So let me get this straight: The kick-backs disappear when you ride with the choke on

?? 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

, 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

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

John · « **Reply #14 on:** October 03, 2003, 07:08:08 AM »

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

Author Topic: Kick-backs for dicussion... (Read 12394 times)

supermotokx

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