The clutch linkage is improperly adjusted.

Adjust the clutch linkage. Refer to Clutch Assembly Adjustment .

The sliding clutch gears are tight on the sides.

Adjust the clutch system. Refer to Clutch Assembly Adjustment .

Chips are wedged between the spline of the shaft and the gears.

Overhaul the transmission.

There is a misaligned mainshaft of the countershaft.

Overhaul the transmission.