I have the same problem with my s-25 one way bearing. I think every engine suffers the same problem sooner or later. One way of sorting it indefinately would be to seal the backplate & the carb asell, if your doing the backplate, you might aswell do the carb. Doesn't mean your one way will last forever, just means that it will stay relatively clean in the short term.

Click http://www.gotnitro.co.uk/showthread.php?t=86 for a little guide on the subject.

As for your spur. Just be carefull if you go with a stronger or metal one, it's better that your spur strips & leaves your tranny or any other parts in tact, rather than the hardened spur not giving way & passing the brunt of the force onto other more expensive parts.