If it has never been rebuilt, it's about time for a top end overhaul. You can check the compression (160~190psi) and inspect the spark plugs (look for oil deposits). If you really want to get carried away, pull the exhaust system and look in the exhaust ports for carbon buildup. I've seen these motors with over 300K miles on them but they're pretty clapped out by then. The cam chains are usually good for about 150~200K miles as long as the tension pushrod hasn't run out of travel. When you freshen up the top end, be sure to replace the rear cam chain guide, the pushrod pounds a depression in the back of it and you will run out of adjustment. You can put the tensioner back in the middle of the range by welding a nut on the pushrod (8mm flange nut works perfectly). When you do a top end overhaul, I suggest that you bore the cylinder to the next oversize and install new pistons and rings. Generally the cylinders are too worn and out of round to just put rings in them. Plenty of people do it this way but they don't last. In about 10K miles they will be back to burning oil. By the time you hone the cylinder straight enough the pistons are too loose and will knock. Also if the motor has been "pinged" for a long period, the ring grooves in the pistons will be pounded out of shape. The top end pictures on this site are from a funeral escort motorcycle with 108K miles on it. The piston pictured is from a Wiseco 1075cc overbore kit that is cheaper than the KMC stuff. That motorcycle just had another top end job @ 200K miles. About the best you can hope for is about 100K miles on a top end, most people get around 30~60K. Kawasaki's specification for oil consumption is 750 miles to a quart of oil. Anything more than that requires a top end overhaul under warranty. Personally I feel if it's not visibly smoking and the engine performs well; just leave it alone. The oil is much cheaper than a top end overhaul. Using a top quality oil will help with the oil consumption problem.