Athena 478cc Big Bore Kit / Reliability ?

I am thinking of rebuilding my engine (03' WR450), and was contemplating putting in a 478cc Big Bore Kit. All i was wondering was will it make the bike any less reliable, or put any more strain on the other components? Any comments from guys who have already done the upgrade would be appreciated too. I have had a quick search about, but cant realy find a definitive answer.


Anyone? Really would like some input before i splash out.. Any help/Advice is muchly appreciated :applause:

Won't you have limited re-sleevs on the motor if you bore it... I really don't know though...

Good question - wish I knew ?

I was thinking about that too..

The WR motors can't be re-sleeved. They are a nicosil plated aluminum bore, so if you go oversize, you must replate anyway. I can't speak to the 478 kit, but I have a Luke's racing 444 kit on my 426, and it has been rock solid reliable. I had an Athena pro kit on my son's YZ125 as well, and it was also pretty reliable...and the one time it did take a dump, Athena stood behind their product and replaced the damaged parts on their dime.

I wish they made a bigger kit like a 525 like KTM has

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