You put the belt on backwards I think. Theres a flat side and an angled side to the belt.
You should look at using a different setup if you keep having issues like this for the future.
Yeah I realized that back then but I’ve gotten rid of the bike since this video. Made a really fast 2 stroke with the parts from the build.
Get a postie
Look into 12g or 10g spoke wheel, no worries about that again. Get a chain cvt.