Torque is not the only variable that increases with increasing compression ratio; fuel economy also increases (half of the reason for the extreme fuel economy of diesels is the high compression they run). But probably the biggest effect on mileage is engine revolutions per mile. The Triumph Tiger, a purely highway bike, is geared for comfortable and economical cruise at moderate engine revs. The lower the revs, the lower the engine friction. The KLR, which has some off-road capability, must have a lower first gear even though it has only five transmission speeds to the Tiger’s six, so in fifth I’d bet the KLR is turning fairly high rpm and generating a fair amount of extra friction loss. Normally, you can expect a bike with fewer cylinders to have lower heat loss (because of lower total combustion-chamber surface area) than a bike with four cylinders. You could see this in Superbike racing, when 1,000cc fours needed visibly bigger radiators than did 1,000cc twins. This effect, however, seems unable to push the KLR’s mpg far toward that of the Tiger.