Have a rotary style carb on a RedMax backpack EBZ7500. I cleaned the carb thoroughly (ultra sonic) and added new kit diaphragms & gaskets. Can't get it to start when cold after purging (working fine) on choke or any other position. But if pull the cord after I add a squirt of fuel down the plug hole, it starts and runs fine. Then it continues to restart easily as long as it's hot. After failing to start it cold, I have checked the plug and it is dry; ie, doesn't appear that fuel is entering the firing area (venturi?). Any advice on solving this problem will be greatly appreciated.