Looking at this link-
http://www.planopower.com/store/honda/hrr216k1s3da.php

It appears the transmission has a lever that hooks to a cable.

I would venture to guess the cable broke or became disconnected.

I wish that were the case. The cable is fine, looking at the drawing of the tranny, item#8, the clutch lever, it moves freely but the clutches either don't engage or they are glazed and just slip. either way its time for a new tranny ;-(

Since the only option seems to be a replacement, you really can't hurt anything by "trying" to fix it.

Maybe a nut holding the lever on loosened up?? Can you feel if the shaft actually rotates?

I didn't remove the drive assembly. Because of how and where it is located the only way I can see if the shaft turns with the lever arm is to remove it from the mower. I'll give that a shot tomorrow.

That's a good suggestion, thanks.

I read all of your posts and thank you for you input. However if your cable is activating the lever on top of your gear box, there is two thing it could be. For me it was both. I removed the rear axel assm. then removed the pan off the bottom of the tranny to find a pile of brass shavings at the bottom. the worm gear was fine but the crown gear, mesh side, was mashed. one trick if you want to save money you can remove the crown and turn it 180 Deg. giving you a fresh side of the gear to use. By the way
, the cause of the problem was that there was about 1 ounce of gear oil put in by the factory. ``how nice``. Anyway I put it back together just to find out that it still slips. Took it apart again and added a washer in with the clutch plated adding pressure when drive is engaged. filled it with gear oil, reassembled the transmission and it works like the the day i bought it.
Or you can just buy a new one. 400.00 dealer or about 150.00 on the net. I took it as a challange.

I ended up replacing the drive assembly. My local dealer charged me $110.00 for it. It was a little of a challenge removing it, I don't think Honda expects it to be replaced ;-)

I discovered on my model you adjust the clutch tension by moving the cable assembly up at the top where it is fastened by the lever. There should always be spring tension when the clutch is engaged. there wasn't on mine and that caused the clutch to glaze and cease functioning.

I ran over a pipe and it shot out and ripped the left rear tire. It also broke the left adjuster arm. I got the parts already and removed everything except the broken adjuster arm. Can anyone tell me how to remove it? Thanks