I was riding my 2002 zr800 efi cc le yesterday , and it was WAY>>>> below zero with the windchill. My guess when your moving on the sled would be 20 below at least. Any how The trails were Mint , and I didn''t care about the temps becase the trails were so good. I got out about 10 miles and it started to bog.I turned around , and it became more frequent .It was just like it was running out of gas. I would have to burp it severely just to keep it going. It finally died near my trailer.Good thing I turned around when I did.I had a full bottle of iso in the full fuel tank before I left. When I got home it started up and seemed to run ok.My sled like a lot of other efi machines has the notorious bog when you hit it hard.I wasn''t running in any powder , just smooth trails ,So there was no snow injestion. I was wondering if this was a smart valve issue ? Would they freeze even with a full bottle of iso ? I saw no frozen fuel lines, And it was decently warm and dry inside engine compartment. I would appreciate any thoughts and/or suggestions as to what possibly may have froze. Hope I provided enough info based on symptoms. THANKS IN ADVANCE!!