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Message: [QUOTE="Rich Rohrich, post: 1480386, member: 16241"] Sorry for the delay getting to this. The KLX is a very simple engine design, very rugged but very simple. It won't care if you use synthetic or mineral based oil as long as it's even close to the correct specification. If you put oil into the cylinder and your noises quieted down the odds Then there is unintended metal to metal contact. The likely possibilities are the compression are fitted with too little end clearance. The compression rings have a small clearance space that needs to be verified in the barrel but off the piston. This clearance is necessary to make sure the ring ends don't butt together as the engine heats up and the metal of the rings expands. If they butt together this keeps the rings from compressing together enough to fit the bore basically making them oversized for the bore due to metal expansion. The manufacturers usually make the rings with too little clearance so they can still be used in excessively worn cylinders. The other thing that comes to mind and what my guess is based on how many times I've seen it happen is the scraper rails or the spacer for the oil ring package slipped during cylinder installation and are now overlapped and doesn't fit the bore correctly. For those not familiar with what a four-stroke piston ring package looks like, it usually consists of one or two compression rings that are similar in shape and function to what you're familiar with on a two-stroke engine. Underneath these compression rings is an additional ring package that consists of two very thin flat spring steel rings that are separated by a wavy spacer. The picture below should make it clearer. When you're assembling the cylinder onto the new piston it's pretty easy to have the oil ring package squirm around a bit and overlap enough to cause the problem you're describe. It's happened to everyone at some point if you put together a lot of four-strokes. As painful as it sounds I'd HIGHLY recommend you take the engine back apart and look for signs of damage to the bore. High pitched noises from the engine that are cured with excess oil are a sure sign of some unintended metal to metal contact, Unusual wear marks will tell you the details of the story that you need. Good luck, and don't feel bad about this. Every great engine builder from the guy at the local track to Byron Hines has been through this at some point. You'll learn from it and be part of a big club who acquired something valuable once you sort it out. [ATTACH type="full" alt="1698329987967.png"]27696[/ATTACH] [/QUOTE]

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