Help diagnosing top end engine noise

I haven't found any evidence that someone tightened down the valve cover without loosening the tensioner. All the guides look good and I have not found any evidence in the oil pan of broken guides. The chain is a bit stretched, but it's at the outward edge of the serviceable limit. The bike has about 80,000 miles and is a former cop bike, so I figure the chain stretch is normal, and not outside of the limit.

Thanks-- I have not checked this. I'll pull the exhaust when I get a chance and see if there's any sign of a rogue guide.

Here's the main thing, though: whatever is causing this noise, it only starts up as the engine warms. The bike sounds perfectly fine when you first start it up, but after ten minutes or so of idling, it sounds like something you'd never trust to ride.

This seems to be the main clue. What do you guys think would come on with warming like this?

If it is a guide it would get loose when hot but they're made to bottom when installed. If it is a oversized one could be installed.
Steve
kzzone.com/resources/valvesguides/guides_1.jpg
kzzone.com/valves.html

Thanks very much. What do you mean when you say they are made to bottom? I don't quite understand, but this sounds like it could be a good possibility.

 

They have a shoulder on them so they can't go too far down. That doesn't mean it wasn't loose and worked it's way down. Only way to find out is to take the head off. You might find a damaged guide in the process.
Steve

wrote:

They have a shoulder on them so they can't go too far down. That doesn't mean it wasn't loose and worked it's way down. Only way to find out is to take the head off. You might find a damaged guide in the process.
Steve



 

The guide 49002-1002 shoulder-stop is a circlip 92036-023 located such that it bottoms the guide at the head surface.
 
I believe the affected guide gets driven deeper into the hole along with the circlip which protrudes just a tiny amount.

images.cmsnl.com/img/partslists/kawasaki...ar092568714_39c7.gif

The sunken guide should be visible with the exhaust pulled away from the head, as it was obvious in my situation.
A Ca. police bike mechanic once told me that those bikes were often left running during traffic stops by careless riders.  They should have been ticketed for doing so. 

Thank you both very much, Steve and Daveo. I'll inspect and see if I can't spot something like this on the exhaust side.

Use a length of 5/8 heater hose as a stethoscope.

Also, when you tightened the exhaust header did you lift the weight from the rear?