Simplicity RTH Series Operator's Manual page 44

Adjustments
Idler Pulley Belt Guide
The idler puley belt guide is correctly adjusted when its edge
is 1/4 inch (6 mm) from the rear edge of the idler arm (figure
36). If not, loosen the nut (C) and move the belt guide.
Tighten the nut and recheck the measurement.
Figure 36. Idler Pulley Belt Guide
A. PTO Idler Arm
B. Belt Guide
C. Nut
42
PTO Pulley Belt Stops
There are two belt stops at the PTO pulley; one on the left
(figure 37) and one on the right (figure 38). With the PTO
lever engaged, measure the distance between the belt stop
and belt. There should be 1/16 Inch (1.5 mm) clearance
between each belt stop and the belt. To adjust a belt stop,
loosen its mounting capscrew, move the belt stop, and
retIghten the capscrew. Recheck the measurement.
Figure 37. Left PTO Pulley Belt Stop
A. Belt Stop
B. Belt