Big Bore Kit

I've been looking for big bore kits for my 04yz450. I found an athena 480cc 98mm kit complete bolt on kit for 659$ I was wanting to know how many hp do I gain from this increase. Will it also have any disadvatages. I am thinking this is a better investment for an increase in hp vs. a 700$ pipe. I already have my suspension dead on and a rekluse so the next upgrade I was thinking is this kit. I have already had my ports cleaned up .If anyone knows of a better deal plz tell me where. The kit includes Athena nickel-carbide plated cylinder, Forged & Coated piston, Rings, Clips, Pin and gaskets.


More of a gain in the Tq dept. than HP. Have had no bad experiences with the Athena kits. Tdub

also dude you will want to change ur jets a bit. Im not sure if its a bigger piston or bigger stroke. But yea it will be more beinificial if you are doing the job yourself. If your not then the shop is going to charge you rediculously.

The Athena is pretty much a bolt on big bore, but if you are not familiar with doing it, you might want to check out someone who can help. Tdub

So this is a yes vs. a pipe?

Alright, can I ask WHY in God's name would you need more power? I bet you're not even using all the power it has now!

Alright, can I ask WHY in God's name would you need more power? I bet you're not even using all the power it has now!

You can NEVER have enuf POWER :thumbsup:

You can NEVER have enuf POWER :thumbsup:

True, but can you use all the power? That's the hard part...

I race cross country and I need some more top end. And a little more "umff" would help me pull taller gearing. Maybe I could actually use 1st gear. When I say more top end it's because most races will have at least once in the track a really long straight that you can top your bike out. It's pissesme off because they make me race open class because they won't let 4-stroke 450s race the 250 strokes and I'm topped out and a pig of a 500 passes me on the straights. The 250 4 stokes race the 250 2 strokes. Nobody in the class does that because it's a huge disadvantage.

PS: Does anyone know about how much it would cost to add a 5th gear and what I would need to do it myself. I don't know if I could swap it with the wr gears because I am in love with the 4 speed on motocross and wouldn't want their ratios changed.

I put a 470 BB kit on my 03. It is absolutely awesome. I purchased it from Langcourt. Price approx 350.00. Suspension is full Enzo and the bike is just perfect for a 03

You will notice more vibration - but the bike pulls and pulls and pulls.....much more than a 450

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