I have talked many times about this "problem" and you got a few solutions...
Easy fix and not soo good,large idle jet and drown the surging,makes low performance at idling though!
Otherwise check up "overclosing" KIPS.Little harder to kickstart,but a good trade in my opinion.
Check for worn slide or worn carburator.
All this surging depends on ignition fire at BDC to "clean out" all mix of resisting fuel/air.
just my 2 cent!