Have a KD510SP with the original chain drive clutch. It seemed like it was binding so I cleaned and oiled it. It turns forward/reverse and engages. My question is how loose (when turning) should the toothed gear turn by hand without a chain/wheels attached. Mine turns with some resistance (its pretty firm) by hand when its not engaged. Is this normal? When I used some penetrating oil and lube it was pretty dirty but it doesn't grind or feel rough when turning. Know its been discontinued and it doesn't look like it can come apart for total breakdown - from what I can see unless its held together with a friction pin.