i know stock they are fine, but how about heavy mod? nitrous? i found a yfz i would like to buy, and i just want to know how these engines will stand up to what some would say is abuse. i want to put a happy button on it (nitrous) with a 40hp tip, will that cause these engines to grenade? do port and polished heads do anything? other than big bores, what is the best way to make power?

 

Well, they are designed for hard riding. I think they would hold up as any other with nitrous. Port and polish most def does something.

 

call up racers edge in az they make the 450s fast as hell

 

i know from experience that it does not take much sand for it to completley grenade a 06 yfz motor i have done it twice make sure if your running k@n to have a good prefilter and it wouldnt hurt to have an extra filter to

 

effff k&n get a fuel customs intake

 

Its the same 450 motorcross motor Yamaha uses in the YZ. I go to to motorcross races every weekend,the motor have to be and are made to be rebuilt after so many hour. You want to play you have to pay.

Want dependability, do not get a motocross based 450 motor (Any brand), get the 400ex or 700 raptor.

If anyone knows a way for a 450 to run hundreds of hour without needing a rebuild,I have many weekend motocross friends that would love to know that secret.