I ran into the vent problem also, though not in the rain. I think it happened when I went through a puddle on a gravel driveway, at the Triumph dealer in fact! I parked, went in a bought my oil and filter, took off, and a half-mile down the road it was like I was running out of gas. The tube must have been just barely clogged, because the bike would sputter, die, restart, repeat. I had an idea that that was what was happening, but it never occured to me to loosen the gas cap. I just limped the mile-and-a-half home and cut the vent tube at 45 degrees. Cleaned out the tip-over valve to boot. Haven't had a problem since.
