I bought a used MTD rider but the only number left visible under the
seat is 1183A AC which I don't think is the model #. The mower's deck
was taken apart and I've rebuilt it but I'm having trouble getting the
drive deck-to-engine belt engagement correct. The deck-to-engine belt
doesn't have an engagement pulley to take up slack in the belt.
Instead it looks like the deck is supposed to swing backwards to take
up slack when the deck engagement handle is moved down by the operator.
There isn't a separate deck engagement handle. The deck height and
engagement handle are the same.

I do know that the engine is a Briggs 42A707, 9601245A which I think
means it was made in 1996 which would date the MTD rider. Also the
rider is an 18hp, 46" cut hydro.

Does anyone know what the MTD model number might be and where I could
find a schematic of the deck to mower linkages? Or does someone have
some tips.

There are a pair of hangers on either side to link the deck to the
tractor and there doesn't appear to be a wrong way to hang those 4
points. Then there is an threaded adjustable hook on one side. And
finally at the back end is a swing arm that goes around the main deck
drive pulley. It looks like this arm might be there to stop the deck
belt when disengaged. The swing arm connects to the tractor via 2
hanging bars and there are several holes to choose from. Also on the
one side is a rod that is connected to the engagement handle. This is
the setup that I think I need to know how to connect.

The belt that seems to fit best is a 5L 58" long.

I went to MTD's website but couldn't find a way to get to the model
number since the one on my machine is faded away-unless the 1183A AC is
the model #.

Thanks
Bill