Will the engine off of a crf 450 dirtbike work on my trx 450 quad. thanks alot

 

The 04/05 quad engine is very different from the bike engine. The 06-08 engine is more similar to the dirt bike engine, so an 06-08 dirt bike engine probably will have a better chance of fitting in that frame.

But...probably not a great idea anyway. Quad engines are beefed up for a good reason. Quads are heavier and put a greater stress on engine parts. Quad engines often have stronger parts in some areas. Trying to see if you can twist a crank????