mysterious noise

[rrpaulsen]

I had my 2001 KDX220 out for the first time this season a few weeks ago. I had stored the machine with StaBil brand fuel stabilizer in the full tank of premix over the winter. Before the ride, I ran the engine a little bit and changed the oil. About ten miles into the day's 60 mile ride, the machine developed a problem:

While decelerating on a steep down grade, the engine began making a loud "squawking" sound. To me, it sounded about like an old electric drill that I had years ago: when the bearings on the drill went bad, it produced a similar squawking sound. The sound on the KDX appeared only when descending a grade, or when closing the throttle after revving up the engine in neutral; never while under heavy load. The engine makes good power and exhibits strong compression. It seemed at the time, although I could have imagined it, that the bike was down on power at low RPM and didn't want to idle. Despite making this horrible racket, the engine kept running through the day, and I made it back to the truck.

I was unable to work on the machine for a few weeks due to my work schedule. Then yesterday, I began to look into the problem. One thought that had crossed my mind was that I might have lunched a reed valve, so I removed the carburetor and reed cage to inspect. I found the reeds to be intact and lively. Using an inspection mirror, I examined the top end through the intake port. All appeared clean and shiny in there, including the bit of piston skirt that I could see. I reassembled the engine and tested it a bit.

I live in a suburban neighborhood where it is inappropriate to run the engine much or ride the machine. Nonetheless, I started the engine and warmed it up. I blipped the throttle from time to time, but could not get that squawk to reappear. Thinking the problem might require a hot engine, I put the transmission in gear and slipped the clutch against locked brakes to get the engine hot. It still would not squawk.

Maybe I need to actually run the engine at higher RPM or under the kind of load that only real riding will produce in order to get the sound to reappear. The problem is that this requires loading up the bike and taking it out to a secluded location, and this is not very convenient.

Sooooo ... what I wonder is: Have you experienced a similar loud squawking sound, engine-related, on trailing throttle, with your KDX? What turned out to be the root cause?

Or: do you have any good tips to help me try to isolate the souce of the problem?

Thanks,
-Ron

 

[Jackpiner57]

Is it possible that the squawking sound was your brakes?

 

[rrpaulsen]

Sorry I wasn't clear on this. This is an engine-related sound. While the initial indication occurred while I was rolling downhill, the sound was present even with the motorcycle stationary. All that was needed to get the sound to happen was to rev the engine with the transmission in neutral and the machine stopped.

-Ron

 

[rethnal]

Do you have your airbox lid removed????? This generally makes a duck like sound when reving really hard under load or quick deceleration.

 

[cfr1970]

You went the direction I was initially thinking. I would've taken the reed cage out and made sure the screws were tight. I'm assuming you tightened them when you had the cage out. The other area to inspect BEFORE your next ride, is your KIPS valve. If you have any problems there, that is something to address before you start to ride again.

 

[gnarlykaw]

I too have heard this noise! yeah, it sounds like a dry engine bushing. it only lasts a couple of seconds, then, it's gone. it may not happen again the rest of the day, or evenn many more rides. but I have heard it. maybe three times............

 

[rrpaulsen]

re: airbox lid. It's either removed or drilled, I don't recall just now. But this is not a consistent phenomenon -- it comes and goes, and I have not been able to duplicate it since the day it happened. I would think that any air inlet noise associated with the airbox lid would be consistent.

re: KIPS valve. I'll inspect it, of course, but as far as "my next ride" is concerned, I can't see going riding until I've determined root cause and corrected it. This sounds like something that could leave me stranded in the middle of the woods.

Any other ideas? Any known problems that come up from time to time with these engines?

Thanks,
-Ron

 

[craig_enid]

I've gotten a couple of 'squawks' out of mine. Both times was during up-hill high-rpm clutch-slipping fiascos when I should have been in first gear, but wasn't. Never found any problems after hearing the noise, I always felt it was the clutch assembly cussing me.
I know that doesn't match the scenarios that produced your 'squawk', but your description of the sound matches what I heard from mine.

 

[SpeedBump]

Crankshaft.

 

[cyclebradd88]

It sure sounds like the stator side bearing to me. I would guess that over the long winter, there was some condensation (or plain old water from a mud puddle) inside the cover that caused some rust. It is also possible, that your connecting rod bearing got some rust as well. (from condensation) Howling is almost ALWAYS a bearing problem. If it walks and talks like a duck, its probably a duck.

 

[JasonWho]

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[KAY DEE EXER]

I think its more of a RATTLE noise. Ive got a 98 200 that runs quieter when I run more oil. Not sure if this is what you mean but mine was closer to a rattling sound. (I think someone described it as sounding like running with a crankcase full of gravel.) Pretty close !!!

 

[fuzzy]

Water pump?

 

[McRider]

Since the bike made the noise in neutral and not rolling, it is probably one of the engine bearings. The fact that it occurs when you have the throttle closed means it is probably due to getting less oil at that time. I suspect a lower rod bearing or maybe a crank bearing due to condensation over the winter as has already been mentioned. I don't understand why you don't get the noise when testing at home. I think you have to find a place to get it warm and see if the noise comes back. You can also take the top end off and spin the crank slowly by pushing up and down on the rod to feel for any roughness. That's kind of drastic, but it's one of the steps in a complete engine tear-down, which may be in your future anyway.

 

[rrpaulsen]

Thanks for the ideas, folks. I've not been able to get back to troubleshooting on this over the past few days, but I hope to get back to it soon. I'll pop the ignition cover off and look for rust/damage/debris. I'll drain the oil and look for debris. I'll drain the coolant and pop the impeller cover off to look for debris or damage. I may pop the top end off so I can feel the rod and main bearings. I just hope that whatever the root cause is, the damage is bad enough that I will be able to spot it (I'd hate to just replace parts at random and never know for sure if I'd corrected the root cause).

-Ron