This morning I decided to pull out my reed cage for a quick inspection. I pulled out the spark plug so I could turn the engine over and quickly peek at the piston too. I put the bike into fist gear and slowly spun the rear tire. What I noticed was a loud, hollow knocking noise at TDC and BDC. I know the engine noise is normal for a KDX. My friends bikes are no louder or quieter than mine. Has anybody else noticed this with their bike? It almost seems like a problem with clearance or a wrist pin. My local dealer say's that replacing the piston with one other than OEM, makes it considerably louder. Has anyone had any luck reducing this noise? Has anyone installed a bige bore kit and have the same noise?

It's probably piston slap.
You should take it all apart and gauge the clearance between the piston and cylinder.

If I understand your description right, you're listening to a normal engine sound.

Well, WOULD be normal under compression.

Having none of that (reeds/plug out), I don't know why you're hearing anything.

Piston/cylinder clearance is going to have to be pretty bad to have the º change of the rod make a noise at hand-turn speeds.

How well does your bike run? When was the last time the topend was serviced?

It SOUNDS pretty serious...but surely I'm missing something.

Actually, the bike runs great! It's never had a top end done, but then again it's only got about 200 miles on it. I'm just concerned about the rapping noise that it, and other KDX's, make. It's just not right.

i could be the valve train..

I don't know why the noise with no compression and hand-turning.

But..if it runs great, don't sweat it.

You are running 92+ octane, right? The kdx is REAL noisy on lower octane fuel. imo and all that.

....not as noisy as 200 pumpkins, though!! Whoa. What a racket!!!