Well today was the first time we had enough snow to use the sleds. The 550 was a bit cranky to start but eventually started and ran. I warmed it up by letting it idle for 4-5 minutes and then my wife drove it around to the front of the house to the driveway so we could top up fuel, oil, etc. She shut the sled down and I fuelled the sled up and she restarted it....ran fine idling until she clipped on the emergency tether...then the sled quit. The tether didn't disconnect but that was the only thing she touched and the sled died. I removed the tether and held the button down by hand and cranked the engine...nothing. Next I removed the plugs and both were wet so dried them off with a propane torch...waved it over the plug holes too but no poof from excess fuel. Replaced both plugs with new ones...grounded them on the screws holding the cooling plastics in place and no spark. Remembered that when it was cranking over at first before moving it that it seemed to start as I was releasing the key from the starter crank position...thought maybe just a coincidence. She started and ran for several minutes....moved it and let it idle fine. I have it sitting inside now in heated garage and will check it again in the morning. Any suggestions would be good. Thought I might try to bypass the emergency off switch so will try that in the morning.