1989 Ski-Doo Repair Manual, Page 260Get this manual
Section 03 TRANSMISSION Sub-section 03 (DRIVE PULLEY)
5, Shim (neutral)
For the neutral adjustment, proceed as indicated belowWARNING: One or two shims #5 are used to obtain the neutral function of the drive pulley when engine is idlingProceed as follows when retaining bolt is torqued: With new drive belt installed, it should be possible to insert minimum of 0.80 mm (.030 in) thick feeler gauge on each side of the drive belt simultaneously pushing drive belt to sit on bearing