NH 451 mower crankshaft assembly (pivot drive group)

[DogT]

The oil seal on my crankshaft is missing after I pulled off the sheave to adjust the bearing. Is that bearing supposed to come off the crankshaft to the rear or is mine just a bit rusty? There was a lot of grass in there. I ordered a new seal, but does that castle nut tighten on the seal the bearing or is the seal just around that bearing. Not sure if I have a 1 piece or 2 piece bearing either since I couldn't get it out. I'm willing to try again when the seal comes. It runs freely with no grinding after setting up the castle nut but no seal and the knife bar not attached.

 

[DogT]

OK, here's how it works. It was obvious once I got the replacement seal. The old seal had come apart, the rubber part fell out, the metal ring was still there. I pulled the old metal ring out from the outer perimeter, cleaned the area, pressed in the new seal, a 2" piece of PVC worked fine once it was started. The castle nut front face bears on the bearing cone and sets the tension. The ID rubber part of the seal, seals over the outer diameter of the castle nut after it's installed. That's it. Done and belt is back on with the bearing/sheave now not loose. I should probably check this at the beginning of every season, it's easy enough now that I've put anti-seize on everything.