F*** the bullshit. Just turbo or twin turbo your existing austrian vibrator and you'll get more explosive power than you'll know what do with. It's cheap when compaired to your build plans and if you keep the boost pressures low then your motor will last a bit longer.
Or if ur mr. Moneybags then import a Eva track 8 from the Netherlands and have a turbo diesel 3 cyl that gets insane has milage. Just be willing to shell out like 26k plus import tax etc.
-Chrome don't getcha home, but carbon fiber sure is fancy
2005 KTM 950 Adventure
2005 Yamaha YZ250F
1978 Batavus 48