If you are using alloy pinions, I find they are much more susceptible to sand/grit damage than steel, which in turn damages the tooth profile, whcih chews the spur. Using steel pinions, the damaging effects on the pinion and spur are less and I usually just have to flick out the odd embedded grain from the plastic spur.
For the cost of 1 pinion, its an fairly cheap and rapid way to test for an improvement.
HTH
