If the belt needs adjustment simply loosen the two 3/4" bolts riding in slots on each side of the thrust frame, leaving the top one snug enough to hold the belt tension after adjusting it.

The belt tension is increased by lowering the whole engine.  Use a large screw driver as a lever from behind the fan to lever down the engine mounting frame by inserting it between two horizontal members of the engine frame and the thrust frame.   Once the tension is correct tighten the 3/4 bolts and run the engine at various r.p.m. levels to check the tracking of the belt.  Do not overtighten the belt and the pulley.

The tracking of the belt is correct when it moves between the pulley flanges as the engine is accelerated and decelerated.  If the belt rides continuously against one pulley flange or the other the angle of the engine needs to be adjusted.

If the belt rides continuously on the pulley flange nearest the engine, the front of the engine must be lowered.  If it rides on the pulley flange nearest the fan, then the front of the engine must be raised.

DO NOT REMOVE THE FANGUARD WHEN TRACKING THE BELT.

Tracking is adjusted by tightening the front of the engine up or down.

Loosen the bottom two 3/4" thrust frame bolts completely and the top two only enough for them to act as hinge pins without releasing the tension on the belts.

Next raise or lower the front engine adjusting bolt, then raise or lower the front of the engine; tighten the 3/4 bolts and start the engine to recheck the tracking at various r.p.m.  Two or three adjustments may be necessary before the belt is tracked accurately.

Failure to make the belt track correctly will cause it to fray and frayed threads may damage the fan blades.