RE: More Rio 51 woes.
Sounds like your not priming it enough to me?,try 1 -2 very slow pulls while choking it then it should pop,then choke off and one short sharp pull with 1/4 throttle and she should start or try to .I had similar problem with my first zen it was only when told this method did it start and i too had sore hand trying before i tried this method hope it works for you.
Mart