clutch engagement trembling, due to the fixed clutch shaft or shaft sleeve spline wear is serious, leading to shaft and suite with loose, slight sliding, even sometimes can not synchronize rotation, so that the clutch work engagement trembling; Moreover, the loosening of the fastening bolts of the fixed clutch can also make the clutch shake when engaging; The third is the disassembly or installation of the clutch friction surface inadvertently stuck to the grease, the phenomenon of skid, resulting in the clutch engagement work when the trembling phenomenon; The fourth is to adjust the clutch when the separation lever adjustment is not uniform, that is, some of the separation lever elasticity is large, and some are too small, resulting in the clutch engagement work jitter.