Revs, noise and 30 year old motors.

So I've got this bike, a kz 550 with about 4k on it when I bought it. Now I have been told that revs are a bike's friend. I put 4k miles on it last year mostly at 3.5- 4.5k rpm. the bike likes it and there's no problem. The past 2 rides i've been riding at 4.5-6 k with a few more redline shifts. when I started the bike tonight to put it away it now has some nasty top end clack, rpm sensitive and sounds like no oil is anywhere near there. I realize that lugging the motor isn't good but the increased wear and tear is gonna cost money and keep me off the thing. Thoughts? What could the clack be and should I keep the revs at 3.5k?

Spend some time checking out your cam chain and it's adjuster.

Do you have a service manual?

I wouldn't say you should keep it at 3.5K but if the oil's clean and the rest of the motor's in good shape using the whole range isn't going to cause any problems.

KZCSI