My PS-5100 is at the local Dolmar dealer now. Bought it used, and it's always been a @#$!&*#$ to start, either hot or cold. Now one of the anti-vibe mounts (on the handle) broke, so I took it in and had a talk with the dealer. He said it should start with 2-3 pulls, either hot or cold. My reply was "O.K., do whatever it takes to get to start like that hot or cold, and replace ALL the anti-vibe parts. No need to call me if it needs this or that part, just get whatever you need and get it starting like that."
I have a 7900 and even when it's 0°F out (it lives in an unheated outbuilding) I can put the choke on, leave ignition off, give it one pull, turn choke off, turn on ignition and it'll start with the next pull. The Echo CS-340 has a primer bulb, and that takes a max of 4 pulls to get it started. That 510 of mine would take 20+ pulls either hot or cold.