To install you need OpenIV, then just open vehicles.img and make sure you are on edit mode and then drag and drop the files in there.
And then open Vehicles.ide and find hellfury line and change it to this:

hellfury,	hellfury,	bike,		HELLFURY,	DINGHY,		VEH@BIKE_DIRT,	   	NULL,	3,	999,	0.36,	0.36,				0.3,	5,	1.0	,0,	noboot

Enjoy.

Credits

Amistech Games- for making the bike
GTA Mods Del Norte- for porting the bike over to SA
CarCrasher730- for porting the bike from SA to IV
emad-tvk- for his GTA V bike mod and it's vehicle.ide line