I have a 09 KLX, just over 600 miles. I've been burning 87 octane until today; I tried the Super Unleaded, MAN....big difference. My engine ran much quieter and smoother.

I know what I'm going to use now.

/Got gas from Shell...
//The fancy stuff....

 

If the bike runs well with 87 octane that means there's room to increase the compression to get more power.
I'm not so familiar with 4 strokes but with 2 strokes we could change the head gasket to a thiner one and that was all.
What can we do with a klx? Change the gasket, get the head to a machine shop to remove some material? Is that gonna change the cams timing to much? How big of a job is that?

 

Base gasket, and head milling will both raise compression due to less squish area, Just make sure you still have valve clearance or it could be expensive.

 

I have ran both Regular and Premium. The bike runs better and is smother with Premium. So I only use that

 

I always Run 92 octane in my bike It just makes more sense. Cleaner comustion, cleaner internals, longer lasting. I mean it is only $0.15/liter more!!

Ken