sluggish from 0 to 10 mph - ch125

[cardiffchris1]

my spouse's 1984 elite 125 transmission doesnt feel like its taking off as quick as it should. it seems like it isnt adjusting to low gear like it should. bike runs well otherwise, 50 plus top speed. seems like the 125 needs help. after a 15 mile ride it started * away from stops and clunking as it took off. my mechanic took the 125 trans apart and cleaned everything up but that didnt really cure anything. its not clunking anymore but it doesnt feel right either. what parts should be replaced? is it just me wanting more than is possible/