I have a couple bikes both with grubee 66cc 2 stroke motors, one rolls fine and the other has this problem you describe with the drag/friction when clutch lever is pulled in. Said motor has 3000 miles, a while ago I opened the left side where the bar and bearing are; well the bearing was smashed/crushed to 2/3 or 3/4 its original width... I found a slightly longer bar than the one that was in there and this alleviated the problem of drag. I didn't have a replacement bearing so that crushed one is still in there, it may come out with a thin magnet but I haven't a magnet to fit in there. I know they have them at harbor freight but funds are tight even for a $2.59 magnet as such for my tool bag! The bike has drag when clutch handle is pulled in and the button is pushed down to hold it in place, however if it is pulled in tight up against the handle, holding it by hand which gets tiring, it rolls easy
Instead of holding it by hand one could wrap a small rope around it a few times... The other bike does not have this issue.
i've also had to adjust the cable numerous times because I found that pedaling with the drag and not having the clutch lever pulled tight against the handlebar, made the cable loosen up and drag was there even with clutch lever pulled all the way in. I replaced the cable to the same effect but the bike is better than the last few months now that I know to hold it in tight when I want to pedal. Running with original clutch pads.