Motorcycle Repair: Engine Knock, piston slap, pin piston

Question
I just bought a used 2002 Honda CBR600f4.  I've run into a bit of an issue with it.  Coming off of a cold start, the engine runs smooth.  Once the engine warms up (a coolant temp of around 180), the engine develops a significant 'knock' or 'ping'.  It's odd, though.  The knocking starts being noticeable at about 3000-3500 rpm, cleans up a bit around 4500 rpm, then gets rough again around 6000 rpm.  It makes the noise at a dead stop or running.  I've tried different brands and grades of gas, I've replaced the spark plugs, and now I'm starting to run out of ideas.  I'm planning on going through it as closely as possible looking for anything that might be loose, but I'm not very optimistic that that is the problem.  I wouldn't think the sound is normal, but I don't have anything to compare it against.  It really takes the joy out of riding when you're worried that you may be causing damage to your bike.  Any thoughts or ideas are appreciated.  Thanks in advance.

Answer
Hi Brian,

I would need to hear and investigate the sound to give an accurate diagnosis.

Try using a mechanic's stethoscope to locate the source of the sound. Finding the area or source would eliminate a bunch of posibilities.

You can hold a tool such as a long screwdriver against exterior engine areas and listen.

I recommend having a local tech listen and give you an idea of what's going on. You can go from there with repairs.


Abnormal Engine Noise:

Knocking:

IC ignitor trouble
Carbon built up in combustion chamber
Fuel poor quality or incorrect
Spark plug incorrect
Overheating

Piston slap:

Cylinder/piston clearance excessive
Cylinder, piston worn
Connecting rod bent
Piston pin, piston holes worn

Valve noise:

Engine not sufficiently warmed up after lash adjuster installation
Hydraulic lash adjuster damaged (worn, seizure, or spring broken)
Air in hydraulic lash adjuster
Metal chips or dust dammed in hydraulic lash adjuster
Engine operated in red zone
Valve spring broken or weak
Camshaft bearing worn

Other noise:

Connecting rod small end clearance excessive
Connecting rod big end clearance excessive
Piston ring worn, broken or stuck
Piston seizure, damage
Cylinder head gasket leaking
Exhaust pipe leaking at cylinder head connection
Crankshaft runout excessive
Engine mounts loose
Crankshaft bearing worn
Primary gear worn or chipped
Camshaft chain tensioner trouble
Upper or lower tension spring trouble
Camshaft chain, sprocket, guide worn
Air suction valve damaged
Balancer gear worn or chipped
Balancer shaft position maladjusted
Balancer bearing worn
Balancer coupling rubber damper damaged
Oil pump chain, sprocket worn


Respectfully,
Mark Shively