Yardman (Cub Cadet) RZT-50 drive belt slipping

[GroundLoop]

Tractor has 580 hours on it. Replaced the original belt with an 8TEN Belt 810-CBL2440T (57" x 1/2") belt and have about the same slippage. Took the tensioner pulley off and the bearing pulley still feel tight. However I noticed about 1/2" of up and down play in the tensioner arm and lots of wear on the pulley track. Took tensioner mounting bolt and washer off and did not see anything out of the ordinary. Seems to me the tensioner arm is not pushing enough force as I can easily spin the pulley with everything together and the belt is easily pulled with little force. Only thing I can think of is the spring but it does not look stretched at all.

I bought a new Stens pulley to replace it just because I heard it is a wear item and it is also can be used on the cutting deck. Might just go ahead and replace the pulley.

Should the tensioner arm have up and down movement? Anyone else have this problem?

 

[ChasHM]

You sure you have the belt threaded correctly? The wear on the idler in your picture looks like it might have been running on the inside (narrow) side of the belt; it's supposed to push on the outside of the belt. The manual (at Yard-Man Zero Turn Mower - Model 17AF2ACP001 | MTD Parts) has a nice picture of how the belt should run on p.33 and the instructions for belt change says to put a 3/8" ratchet in the square hole to give you enough leverage to pull the idler back, so it sounds like the tensioner isn't doing its job. Is the tensioner spring hooked in the right places? Usually the springs don't get stretched, although replacing it isn't very expensive; my failures have been springs breaking.

Yes, the idler bearings wear out after a while. Usually you won't know till the bearing self-destructs. I wouldn't worry much about the arm up-down motion. The parts diagram shows a shoulder spacer on the idler arm pivot screw; is this missing?