The sprag bearings in the clutch ride on the smooth bearing surface of the gear. If that surface is not baby butt smooth it has already lost it's surface hardness. The new sprags will wear into the bearing surface causing more wear on the gear's bearing surface and then wearing the sprags to match...
Replacing both at the same time starts out with both having full surface hardness and so very little wear occurs over time. Replacing only 1/2 of the pair, with even minor damage to the other, guarantees that you will be replacing one or the other again sometime in the future.
In your case, in order to minimize the likelihood of future problems, I'd buy the new gear and a replacement sprag/spring kit - start fresh with full surface hardness on both halves.
'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'02 Honda 400ex, DiamondJ +3 A-arm widener, Lonestar anti-vibe
Last edited by QuadManiac; 01-18-2010 at 02:54 PM.