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Old 12-01-2012, 03:10 PM   #39
Beastly Adventurer
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Joined: Nov 2006
Location: Spacecoaster FL
Oddometer: 7,390
Originally Posted by beergut View Post
KTM 640adv:
625cc, 54hp

KLR 650
649cc, 20hp

Honda XR650
644cc, 30-35hp

Suzuki DR650
644cc, 43hp

All of these are estimated and from QUICK google searches and are unmodified engine ratings. One thread said the XR can hit the 45-50hp target pretty easily, the DR isnt far off and the KTM makes everyone laugh.

WHy does the KLR suck so bad? What can make serious improvements?
Your numbers are a bit off. Some are crank figures and some are wheel figures. That said, some engines have WAY more volumetric efficiency than others.

The KLR likely has a lower compression ratio, worse flow (through the intake, head, and exhaust), a less-aggressive cam, longer stroke, poor spark placement, poor carbing, or more parasitic drag. It's also heavier than most.

I see a similar difference in power between my GF's Suzuki SX4 and a Honda Civic SI. Both are 2.0L, DOHC, 16V motors. The SX4 makes about 140-145HP at the crank and is a little over 2700lb. The Civic SI is rated for almost 200HP and is a few hundred lb lighter.

If you want to make power with a KLR, improve the flow (intake, head, and exhaust), bump up the compression, put in a more-aggressive cam, use a lighter piston, and dial in the carbing. Other than that, you could increase the displacement with a big-bore kit, and/or add forced induction (turbo) and/or nitrous. A kit exists to make 50+WHP with a WR250R/X, via turbo. Forced induction and/or nitrous can add crazy power. It can also obliterate your engine's internals and your driveline parts.

Forced induction is especially nice at high altitudes.
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