Could be too much slack in your cable. Look at the arm on your engine case - you should have a little bit of free play in the lever on your handlebars maybe 1/8 to 1/4 of an inch at which point you should then see the arm on your case moving a bit which then seperates the clutch. Alot of bikes have a small shaft and ball that run throught the clutch basket mounting shaft that push on something to seperate the fiber and steel plates. These can easily be overlooked during a rebuild or the pivot pin/arm that works off the ball and shaft could be worn.
Lastly either plates could be worn unless you checked them or the innner and outer basket even when the plate seperate are not allowing the assembly to turn freely. This can happen when a washer is left out or installed incorrectly, it will bind or lock the inner basket to the outer - I have seen this firsthand.
Check the obvious first including corrct type and level of oil.
3wheeler or not I'm happy to try to help
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