450F ball park HP numbers and top end rebuild

jft67x

jft67x

My 450 is getting a new top end, accept this time im going to an athena 490cc big bore kit, a stage 2 hot cam, Staneless valves? and some head work. I have 0 experience with the 490 kit and I wanted to know if anyone has tried it with a similar cam set up? The big bore kit says its around 60hp once bolted on, and I will be runnih PUMPGAS (97) is this true?
http://www.crfsonly.com/catalog/product_info.php/cPath/24_39/products_id/962
http://www.crfsonly.com/catalog/product_info.php/cPath/24_39/products_id/898
 
cleonard

cleonard

I have no experience on particular setup, so what follows is based on general experience. Could be totally off base, but I doubt it.

Why is everyone so hung up on hp? It really doesn't matter. What matters is torque. I imagine that the 490 kit is simply a larger diameter piston running the same crank. Larger piston means more area for the combustion gases to push against which makes more torque. This is more torque starting down at they bottom and staying until the high revs. Now between the heavier piston and heavier stainless valves you will lose a bit on the very top end. If you live on the rev limiter I wouldn't even install the kit as it will not be good for engine longevity. Then again living on the rev limiter on a 450 would be totally insane so I really doubt that is an issue.

The hp gains are modest, but the torque gains at the low to mid end are very real. Expect to notice the difference everywhere.

One question. Did you not have enough juice with the stock engine?

Come to think about it, that is a stupid question as I just purchased the beta 520(498cc) instead of the because I wanted more low end torque,
 
jft67x

jft67x

The motor is not stock, its got a heavy dirt track crank and some ungodly huge flywheel. the motor has no where enough power stock. high hp is needed on flat tracks. I will also be going to a hot cam and having head work dome, and maybe a stainless clutch for added inertia
 
HeadTrauma

HeadTrauma

I bet not, especially shopping at CRFs Only. I poked around holy cow, is that what CRF450 parts cost? :shocked:

How important is an exact power number? Racers often spread misinformation to distract the competition, which includes mentioning power figures.
 
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