94 octane stall

I went dirtbiking with a few friends several years ago and my buddy Dans bike wouldnt start... We had just ridden a few days before and his bike ran fine. The only difference was that he put 1 gallon of gas in that morning. His bike has a transperant type of desert tank and you could see the parting line between the water and the fuel !
We drained his tank and refilled it with some of my fuel.
RINGADINGDING..... BRAAAP!!
started right up!