You can indeed change fork springs without removing the fork legs, but it will be impossible to check you have the right level of oil and air gap doing it this way. Different springs, both linear and progressive, displace different amounts of oil/air and require different size air gaps (oil levels) in order to perform at their best.

The Hyperpro springs require thicker oil than OE, so the original oil will have to be changed anyhow, and you'll never get it all out unless you invert the forks and pump it out.

This one of Kev's threads may be of help if anyone's thinking of refreshing their fork oil or changing springs...

http://www.xt660.com/showthread.php?t=4274

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