Not all the parts were existent. When needed, parts were redesigned to improve performance. For example, radiator capacity is up for better cooling, the connecting rod big end and bearing are wider, and the cam surfaces were revised for increased durability. The header pipe was extended and a resonator chamber added to boost midrange. A slim, new 2-gallon gas tank was fitted with the YZ450F’s fuel pump. The air filter, muffler, instrumentation and rear wheel all look like they came from a WR parts bin.