Big Bore YZ450f?

I was wondering if anyone knows anything about the Athena 485cc Big bore kits for the YZ450f 2006, Are they reliable, how much HP? Would i need a bigger carb?

u really need that much more power?

if thats a case i wold just say ktm505

going by his avatar picture, he might want it for supermoto, so he might need the power for that. Or he might be a big boy that needs lots of power to haul him around. The best thing about a big bore yz vs. the ktm, is that you're not stuck with a ktm.:banana:

He might just like overall effect that displacement has on things.

I don't recommend doing big bores unless you are a motarder. I have done them all to my previous bikes and found that the longevity of the motor goes down. Train a bit harder, dial in your suspension and ride more, you will get faster.

But if you do, go with thumper racing. They have great quality stuff.

i got an 05 with an athena 478 kit, hot rods crank an TLR performance ported and polished my head for top end along with a valve job. the athena piston fit the yamaha crank but not the hot rods, had to get the piston machined down.

What way did you have to machine the crank piston?

A WR/YZ crank uses a 18mm wrist pin where a YFZ Quad crank uses a 20mm wrist pin. Is it possible the HR crank you got was for YFZ?

And I am unsure how a big bore would affect the reliability of an engine, I have never seen evidence of this. What I find is most do more at the same time, like cams/headwork etc and then rev it harder. I see no reason going up in capacity slightly would make anything less reliable.

I am currently building an 05 WR with YZ cams, big valve head, Athena 480, JE 13:1 piston, bored out carb. Will let you all know how it goes.

the wrist pin fit fine, it was the part of the connecting rod that was hitting the underside of the piston. this had to be a machining mistake by hot rods and when i called them to tell them, they said that it was probably the piston. I told them that the piston fit on the stock connecting rod and they stuck 2 their story. the hot rods crank was supposed to be to factory specs, apparently not.

the thing i noticed most about the big bore was it improved my throttle response, but when u get into the revs the bike screams and i cant stop grinning. the head work is awesome. i did send my carb out with my head and TLR flowed them together and i havent had to touch the jetting, but florida is all pretty much the same elevation.

good luck with it, keep us posted. interested 2 know how she runs

You must slightly increase the rod small end when using a bronze bushing. The Hot Rods will always clear the OE piston. The Athena crown thickness must be greater than OE. Never heard this problem with CP, Wiseco, or Vertex.

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