It does have the big idler spring. It seems fine and the belt seems to fit on fine with good tension.
For those of you running the same machine, an exmark turf tracer with a 17 hp, can you/do you run at near top speed when mowing on a 7 day schedule? I try and run between 4 and 6 speed if I can get away with it. But if the grass is very wet or any kind of thickness, then i'm no longer able to.