sooo im working on my go karts , and when the vehicle spawns, it appears like this and when i turn, it rotates very weirdly Excuse the mesh spazzes. its the rear lights. Also, this is what the mesh looks like in blender as you can see, the center is in The Center, aswell as everything else. The lights, seat, wheels and steering wheel seems to move just fine, its just the dang body.
Even though it looks like your object is centred properly, try CTRL - A and click apply location. Do CTRL - A again and select rotation and scale. Then export again.
If your mesh spawns in the wrong orientation/position/size it's probably a need to apply stuff (location, rotation, scale) as mentioned by @Inertia. If your mesh is moving unexpectedly then it's probably a result of either mapping poorly to the jbeam OR just a broken/bad jbeam. Please show us a picture of your jbeam (CTRL+B and CTRL+NUMPADMINUS - press this second one repeatedly until the mesh goes away). Very neat idea BTW.
thank you for your help. I honestly think I've made one of these before and just forgot that that was needed, because it sound familiar.