I also just got a klx300SM and have been fishing around for parts. There isn't much!
So far I lowered it front and rear, got a rear rack (Amazon), ditched the rear fender (TST Industries), and installed an exhaust (Delkevic, FMF), and alloy sportbike clip on bars (ebay).
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There was hardly any choice for exhausts. I got a Delkevic because it comes with a bung on the midpipe for the O2 sensor. Then I added an FMF Megabomb header for more low rpm torque.The 8 inch shorty muffler is insanely loud so I made a quiet insert to tone it down.
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The clip on bars are my own adaptation to an unintended purpose. They attach directly onto the protruding tops of the front fork tubes above the triple, when I lowered the front 2 inches. I lowered the rear by removing the shock preload and adding Koubalinks. Each mod has reduced the weight. So far the curb weight is down to 295 pounds.
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