I have issues with high fuel consumption myself. When bike was new I got 27-28 kms pr liter. Then I put both Kev mods, KNA airfilter and changed gearing from 15/45 to 15/48 and got 24-25 kms pr liter with that set up. After a long overland tour and after a full service I know got only around 20 kms pr liter.

Im a relative lean rider, seldom pass 100 km/h and on highways most often ride around 90-95 km/h. Have checked all that I can come up to check. And bike has had another full service but still the same fuel consumption. Other EFI 650 bikes easily gets +25 kms pr liter so Im very disappointed with the Tenere...

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Suzuki AC 50 -78 owned from 83 to 84
Kawasaki Kh 100 Es 81 owned from 84 to 86
Honda Transalp Xlv 600 -97 owned from 01 to 05
Honda Nx 650 Dominator -98 owned from 07 to 10
Triumph Tiger 955 i -01 owned from 10 to 13
Yamaha XT660Z Tenere ABS -11 owned from 2013 and present bike.
Honda Crf250L -12 my bike in Thailand.