Sounds like you would have bad adjustments in your carburator, but since you probably have not changed the mainjet it is unlikely.

Did you change the sparkplug or did you just clean it?

Can you rev the engine with transmission in "0" position, that is without first gear hitted on?

I probably would reclean the carb very carefully first or use a tool to check the voltage level from somewhere, while revving the bike in zero gear and seeing it stalling.

However I am very far from expert.