If I wished to optimize KLR engine performance, with adequate resources, I'd install a second oversize Woessner piston. Raising the compression ratio remains a tried-and-true horsepower increase; yes--premium fuel may be required.
I invoke no logic in my opinion, beyond . . . is it LOGICAL to hop-up a KLR650 at ALL?
Just for discussion: Why, indeed, hop up a KLR650? Don't see KLRs typically in Moto-Cross, Hare Scrambles, Flat Track, Drag Strip, Speed Trials, or other competitive circles.
Hop it up (tuned exhaust, trick cam, custom fuel (carburetor) delivery, ported-and-polished head, degreed (and advanced exhaust) cam . . . Then, whatcha got? Something to go down to Main Street on Saturday night and drag the Harleys at the stop lights?
DISCLAIMER: No value judgment intended. Just askin'!
Just an example; this calculator says, going from 8.0 to 12.0 compression ratio raises horsepower by 12 percent.
I somehow lost my link to the calculator, but the chart accessible from the link provided below is rich with examples:
Compression Ratio Increase vs. Power Comments
Stock, I think the KLR650 compression ratio is 9.8:1. The chart shows (round off to 10.0 compression ratio) power increases with respect to compression ratio increases.