shimmy
Dave,
Try posting in the RV4 specifc topic for better results. Also, there's an RV4 yahoo user's group.
That said, the gear legs are supposed to get wooden dampeners. Many builders don't put them in. Do you know if your plane has them ? I bought an RV4 and plan to add the dampeners. The shimmy doesn't happen all the time and often it takes me by surprise (very annoying).
Good luck.
John