After flattening the lock washer I was able to loosen the nut with little effort. I got the clutch off and it looks like I am missing the o-ring 93210-09525-00 on the push rod. I did have some clutch related noise - maybe this was it. Too bad I already placed an order for the other stuff. I wonder if I can find a suitable O ring at an auto parts store? The primary gear came off next. The key has wear marks and the keyway looks to be a bit worn. A replacement key is on the way. Here is a video of some of the other possible causes of the engine noise. https://photos.app.goo.gl/PnLqahaBDP8HcdTX8 Next up will be removing the balance gear to check the key. Although there does not seem to be any play there.