Hi, welcome to 3 Wheeler World. Read through this post, there were a few good ideas in there. The brake drum just gets stuck on there and as you know can be a big pain to get off.
Most of the time lots of pounding and PB Blaster has worked for me. There was one stuborn one that I had to make a puller for though. I took 3 anchors that are used in foundations (they look like a big "L") then drilled 3 holes in an old rim that I mounted to the hub. I hooked the anchors in the drum and then put the other end that is threaded through the holes in the rim. Then after tightening then all evenly a few turns the drum poped right off.
1984 Yamaha YT 60 Tri Zinger(current project)
1983 Yamaha YTM 200 (rear suspension kit)..... long term project
2004 BMW R1150R
1972 Honda CT 70
2007 Lifan 110