I have almost finished putting a beat up KZ550 LTD back together for my kids to learn to ride on. I have made several test runs to make sure it is okay, before I turn it loose with them on it.
During my test runs, I noticed the RPMs seemed a little high for the speed.I also noticed what seemed to be a whine coming from the bike.
How do I tell if the clutch is slipping? I have replacements plates for it, but I don't want to take it apart unless I have to.

 

Check if your adjustment nut is set correctly on your clutch lever first. If it is, you may need to adjust the clutch "push rod" or whatever you call it on the left side cover. If your KZ is anything like mine, there will be a small rectangular plate with two screws covering the adjustment rod. It doesn't take much wear on the clutch before you will need to adjust that rod. The rod I believe has a slot at the end you can turn with a screwdriver, and a lock nut keeps it in place as well as a snap ring.

Note: If the 550 engine does not have what I'm explaining, let me know.

Hope this helps.