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2011 CRF450R Fork Springs and Oil Volume

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Ok guys, my dad just picked up a 2011 CRF 450 R and it came with the stock 0.46 and 0.48 fork springs and has been revalved by Factory Connection. He's 240lbs and I knew he would need some stiffer front springs so I called up FC to see what they recommend. 

FC said that the 0.48's are good for a 215-225 lb rider. That sounded a little odd since I know most folks complained about how soft the bike was stock, so even lighter guys were going to a 0.48-0.49 spring. I figured with that said, they would have recommend at least a 0.51 or 0.52 for my dad's weight. 

FC also said that in order to use stiffer springs than the 0.48 springs he currently has, that they would need to machine the spring seat. Apparently the springs they use that are 0.49 and up have a larger coil diameter.

My questions are:

Will the 0.49 springs out of a stock 2012 CRF 450 work in his 2011 without getting the spring seat machined? Any heavier guys (220+) used a different spring manufacturer that may not have to machine the spring seat?

Lastly, I'm wondering if he can help out his situation by just adding 10-20 cc more of fork oil. FC recommend 370. Anyone use upwards of 380 or 390 with any success?

Thanks.

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Maybe FCs valving will hold it up better in the stroke. But God damn, .48 is soft for someone that big. That is what I am running, and I am a mid pack 175 lb B rider.

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When they say "machine the spring seat" they are machining a new groove in the damper arm to change the preload on the spring by moving the seat one way or another, my guess is higher for softer preload with the stiffer spring.

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Dont forget that Honda started f'ing around with the unit of measure. a .48 nm spring is more like a .49 kg/mm (which is what we're used to)

 

Racetech offers a .52kg/mm spring for that fork. Its 44mmOD X 460mm long. Factory connection doesnt even offer a spring for that fork stiffer than .48kg/mm. The 09-2012 fork all use the same sized spring.

 

Factory Connection is probably moving the spring seat to increase the preload.

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