03' KX 85 ? engine noise

The knocking or pinging sound you are getting may befrom pre-ignition. You can cure this with getting a higher octane gas. My rm 85 runs fine on premium so that should be okay for you if your bike is stock. You may also want to check to be sure your cylinder and piston are in good shape. I just did the top end on mine and it has twice the power. I don't know for sure of the compression, but your manual should tell you

I have an 01 KX85 and when it started knocking my son noticed it and though it still ran OK it was lacking bottom end. It turned out the powervalve actuator broke. Probably because the powervalve itself got stuck. I think the 03 has a newer design so that the actuater wont break when the powervalve does get stuck. I would recomend replacing the powervalve when doing the topend. Also check the wear an the cylinder where the PV slides back and forth.
John

I have a 1993 kx 80 and I kinda hear the same noise but it sounds like it is vibrating but everything is tight, like all the engine mounts are tight and everything. It also sounds like it is just as loud as the exhaust is that normal.

Noisy KX85

Hi - We've run a 2001 KX85 for the last two seasons and I don't think you should find the engine noise excessive if all is well.
If the clatter or chatter is not pre-ignition, the timing is correct and the powervalve operating freely then I would suspect wear in the cylinder. The plating on Kawasaki cylinders is pretty thin and unless you change pistons and rings frequently (12 hours) you can get wear on the leading face of the piston and excess movement serves to give the plating an even harder time.
Standard Kawasaki pistons run in a loose bore develop stress fractures that spread from the piston boss around the skirt and this flexibility allows additional free movement and exacerbates wear even more. If you run a non-stock piston ensure it has two small oil holes drilled in the leading face to line up with bridge of the exhaust port. This provides improved lubrication to the bridge area (where most wear occurs) and extends piston life.
I'd suggest examining the bore and checking the condition of the plating. If its worn get it replated with a quality finish such as Apticote.
The only time our engine made excessive noise was when the water pump bearing seized solid. This emits a very disturbing wail and leads all the 'experts' in the paddock to tell you the main bearings have gone or the big end is about to seize!
Hope this helps,
Martin Cole.