KDX top end noise

[rvguy]

I've always wondered why my KDX has so much top end noise. It's not bad, but slightly embarrasing. No other bikes seem to sound like this. While out riding at the local State trails, I found 6 other KDXers all of which sounded just as bad as mine. Only one guy with a brand new 220 didn't have this noise. I'm glad to know that this is normal, but wondering what it is exactly and has anyone eliminated the noise.
Here is a list of what I've been told it is. (Everyone has a different opinion).
"Ignition timing problem"
"Normal KIPS noise"
"Carboned up KIPS noise"
"Combustion noise heard through cylinder wall"
"Noise from the rings slapping at TDC"
"Because of the variable compression"

Can anyone maybe narrow down these opinions?

 

[KelvinKDX]

Narrow down the list - why would you want to do that? :D

You need to have some impressive technical explanation for the clatter - for when people ask you why your bike is making such a racket.

... OK - so maybe i can not think of a good one at the moment but i am sure as a group we can come up with some wild ones.


Oh - and the guy with the 220 that doesn't make the noise - i'd be worried. :eek:

 

[23jayhawk]

The hyperbolic honengizer can clatter a bit when cold ... :cool:

 

[G. Gearloose]

Good one!
how 'bout;

The Unobtainium Connecting Rod has a non-typical Harmonic ;)

 

[rvguy]

Thanks for taking me seriously guy's. But I guess that's to be expected from an engineer (all 3, what are the odds?). Normally answers from engineers are over my head and longwinded (do you guy's drive trains?)
Maybe I'll just take this opportunity to thank you and you fellow engineer friends for making my business so lucrative.

Can I get a serious answer?

 

[23jayhawk]

Well, if I have to be serious about it, my best answer would be that it comes mostly from the KIPS system. The sub-valve drive gears have a couple of 90 degree direction changes, and those are never quiet. Also seems like it has an unusual amount of piston slap when cold. So much that when I start it in my driveway, I am almost embarassed at the noise. :eek: The exhaust is quieter than the average weed eater, but the gear & piston noise sounds like a high school shop project gone bad.

I just think of it as the 2-stroke equivalent of solid lifters in my old Boss Mustang...

 

[gooby]

what 23jayhawk said.that's also what a kawi tech at my local said it was ....kips .i never noticed it till i bought one of my own,i rode other peoples bikes.first thing i heard after layin out cash....i freaked then heard the real deal. tip: brainwash urself not to hear it :)

 

[rvguy]

I think I'll just tell myself that it's an audible tachometer....
I just wish I could count faster!

 

[gnarlykaw]

does the noise change with the clutch pulled in?

 

[Robcolo]

The noise decreases with the clutch pulled in --but not any of the top end racket. I just replaced the bearing behind the clutch with a closer tolerance bearing hoping that it would help the clutch noise problem but no dice. The trans input shaft [clutch shaft] is a VERY loose fit in that bearing. I believe that the shaft with it's heavy unbalanced clutch assy. out on the end is simply "flopping" around in it's bearing. The only practical remedy would be to try aluminum discs & see if a lighter assembly would vibrate less.

 

[TechKid]

That noise is not from the bearing, its clutch basket chatter.If you look on your basket you'll see wear ridges from tthe clutch plates on your basket.

 

[Kwackers]

rvguy - I share your curiosity and took an engine stethoscope to my rattling KDX, the greatest volume of noise is on the LHS at the KIPS cover. This may be just because the chamber behind this cover is acting as an amplifier but my theory to add to the list is that it is the pressure wave from combustion pinging off the cover. If you don't have a steth - try a long screwdriver placed against the case and the handle in your ear - you will be suprised how much you can hear going on in your engine !

 

[KelvinKDX]

Originally posted by Kwackers
... - try a long screwdriver placed against the case and the handle in your ear -

sorry Kwackers - i just had to smile while i read that. :) I just pictured rvguy sitting there with a screwdriver sticking out the side of his head. :eek:

 

[Midhigh]

I just signed into this site. I riden a 1983 KDX 200. And never understood that noise. Just purchased a awesome mint 1996 KDX 200. It does the same thing (thanks Steve). When my friends ask about the noise, I just tell them they will never hear the clatter as far dehind me as they will be.

Mike

 

[rvguy]

You know, I used to use a screwdriver until I inadvertantly stuck it into the front of an atlenator. It went clear across the shop and bounced off a techs tool box. After that I bought a steth and a "Chassis Ear".
The Chassis Ear gives me 6 channels to listen to 6 different areas. I just haven't had the time to fiddle with it.
I appreciate the input guys, even the ones from the "special" people in this forum.

 

[KelvinKDX]

Originally posted by rvguy
I appreciate the input guys, even the ones from the "special" people in this forum.

Hey, was that aimed at me? :think:

 

[PowerStroke]

My buddy just had a brand new kdx220 with severe knocking on top end. It was a factory defective wrist pin bearing. He said it was missing a needle. Also another had a KDX200 with many hard miles that knocked like crazy and even though no real wear on piston a new piston and wrist pin and bearing cured it. Maybe the stock pistons have a bit much clearance in the wrist pin area? We all suspected it was the KIPS and were quite suprised. He didn't even had broken teeth in kips. Just a piston pin bearing. MMMMMM

JR

 

[rvguy]

KelvinKDX,
Only if you consider yourself "special"..........

 

[Aaronkdx]

Hey, do you think it sounds like tapping or banging? Because mine does that and I'm worried. Does it sound like something is just rattling around in there, but it always has the same timing.

 

[89kdx200rdr]

its clutch noise. when i was riding the 89 and my buddy on his 04 would stop next to me i would hear all kinds a funny noises the sounds were mixing. if it keeps moving forward keep giving it gas