05 Heritage, under load the engine will turn over a few times and then starter disengages and grinds on ring gear. Can watch drive in the ring gear move to disengage as engine compresses then fully engage off compression. Pull spark plugs, no load, drive will stay fully engaged. Replaced the starter clutch. Cleaned and relubed all gears. Cleaned all contacts, new 310CC amp batt. Same problem. Have looked for new solenoid. I think a problem with hold in under load. It does not look like solenoid is replaceable on this starter. Or could the starter shaft be worn enough to cause starter to act this way?