Mine will has done that twice now, the right side will fire when i start it but the left wont, but i easily fix it. The next time it does that pull out the choke and it should start pinging like it should. Mine acts like the plug is fouled or its not even sparking, once i pull the choke out, it starts right up, then i give it gas and taping the throttle and she runs fine, see if this helps at all