I looked things over the other day and was hoping the reason it wouldn't pull a hill was that the drive belt was well worn. I found this thread and after reading what was going on there, thought a new drive belt and adjustment may bring this back to usable again. So I made a trip over to TSC for the new belt, a 1/2"X53. Also picked up a muffler I hoped to make work.
Here's a pic of the innards hiding under the seat.
The old belt next to the new. I think it had seen better days!
Here's a another pic after the adjustment procedure. If you look at the double nuts at right/center, you can see how much that was changed compared to the first pic. It took a bit to do all this as the SM has this procedure on 4 pages and several pics (that are just a little dark to figure out).
Here's a pic through the muffler.
I cut the inlet off and capped it. Cut a hole in the side and added the new inlet tube I got at O'Reillys that fits the exhaust perfectly. 1-1/2" ID exhaust. I added a brace at the opposite end that attaches to a bolt for the PTO. Shot some of the galvanized paint I had on it. Think it looks pretty good and does quiet it down some.
This is the hill it refused to pull the other day. I went up it at 1/3 throttle, came back and parked it for the pic. Then it climbed right on out, all in 4th gear.