Sounds like my run back from Portsmouth 2 years ago, it started as I came off the ferry and rained like it couldn't keep that bad for more than a couple of minutes, for all of the 2 hour run home, I couldn't believe that the bike would keep running, but it never missed a beat, then sat ticking over happily on the drive. What I did find was that it had sucked a lot of water into the oil and it was completely coffee coloured, so I had to do an oil change.