Was riding yesterday and starting hearing a faint "gravel" road sound coming from the ski - I know, I know it's a bad description but I can't think of another way to describe it. It only happens from about 3500-5500 rpms and only when I hold or slowly increase the throttle. I think it might be the pump bearings but I'm not sure. Anyone have any thoughts or can you point me to a "how to" on a pump rebuild.

Ski has about 100 hrs and don't think the pump has been rebuilt.