Game crashing when trying to use own mod

[Jonny_NOS]

recently i started making my own bike (yamaha dt 125) in mx bikes. i made the frame and tank in Blender, and tried to use it in game for testing. I did everything as stated here: https://mxb-wiki.com/bike-creation-guide/. I can see the bike ingame and go into practice with it, but as soon as i go out to the track my game crashes.

Does anyone have a solution for this Problem?
Thanks in advance!

(screenshots attached)