Problems using joystick

[Breaaad]

(My game is modded, but this doesn't really have anything to do with mods. I hope this is still the right category. First post...) I recently bought a joystick (Speedlink Phantom Hawk) and it works great with the game except for one part. The stick has a built in throttle.. thingy (Let's call it a lever) which is steplessly variable and the input is recognized by my PC as intended, when checked in the system settings. But when I bind the throttle axis to this lever in the game it acts all weirdly. When I push it up to 100% the ingame throttle is around 70%, when I move it to 50% on the joystick, it's at full throttle ingame and so on. Is there anything I can do to fix this? I've tried playing around with the dead zone and sensitivity but nothing really worked.

Thanks in advance!