Engine Wear

I have a 02 400 exc that runs perfect. I ride in eastern Kentucky. Real tight woods riding. I have had my torn down once and had new rings put in it. That was about three years ago. Other than that all I have done is changed the oil, plug, and valve adjustments. When should I think about having the motor pulled down and a new piston and rings put in? I ride quite a bit. However, I do take care and maintain my bike.

When it starts using oil or you run out of valve adjustment. Might want to keep an eye on how many clicks out the cam chain tensioner has left, too. Less than 2 would get me buying parts.

Gaurenteed your intake valves are used up, ring getting marginal. The proper way to test is called a "leak down test" second best option is a compresion test. On compresion there are two way to do it;

valves adjusted normal it should have 115lbs.

The Exhaust valve adjusters loosened 1.5 turns, (this deactivates the automatic decompressor) should have over 175

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