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