"tightened all the way" may be the problem. You need free play both with the clutch adjustment and the cable.
1st) Loosen all cable adjustment. 2nd)loosen the 6mm nut on the clutch cover, gently seat the screw then back off 1/4 turn.
Adjust the cable with some free play at the lever.
Honda parts are available.
This clutch adjustment always seems to be up for interpretation.
So loose the adjuster at the lever and clutch actuator arm on the case.
Loosen the 6mm nut, back out the adjuster screw, gently seat the screw until a slight resistance is felt, then back off 1/4 turn.
Then adjust the clutch arm and lever for 1/8th to 1/4" free play.
That's it???
I'll give it a try. With WOT spirited acceleration I'm get'n a bit of slip before grip from my clutch.
TIA,
Kenzo