I was cutting yesterday in the heat (was about 90F), and once again had hot start issues. My saws are clearly vapor locking, as I have to full choke them to get them to fire briefly, then I take off the choke and they'll run for a moment and stall. If I pull them many times on full choke then I can eventually get them running again - they don't flood. I always try to set them down in the shade, and not to let them run out of fuel but rather let them idle a bit before shutting them off, but I still have issues with it. The saws with purge bulbs will pump vapor when hot - basically the purge becomes useless, but all works fine again when cooled off. Most of my saws have done this in the heat, and they run fine once I get them going and the lines get cleared out again. Given the variety of saws it is not something to do with the saw design, it must be the fuel. I'm using E10 from the local station with good oil at 40:1. I thought once that this was due to winter fuel blends used in the spring on early hot days, but it's September now so this is unlikely. It may be that they've changed fuel vapor characteristics now that no cars have carburetors, I have no way to know. Anyway, is anyone else experiencing this? I can't be the only one having hot start issues in the heat. I'd like to understand better why this is happening now.