If your saying it’s sealed and FULL, you should be o.k. If it is just capped and has airspace where condensation can form repeatedly, I wouldn’t run it. If it is a virgin drum you can run it at least for practice. If your in doubt, give it to Brad or one of the track owners to burn in the rentals. I probably would not run it in a race setting either way being 2 years old. Also, I just mix 2.5 gals at a time to keep the oil suspended better. This is pretty critical for a leaner mixture like a Rotax runs. There are exhaustive threads from techies who have beat this subject to death on http://www.ekartingnews.com/ Make some popcorn and perform a search, you’ll be surprised!
These are just my thoughts, not coming from a chemist or chemical engineer.
But I did stay at a Holiday Inn last night!
And I did have flame out in a helicopter in the mountains of Alaska (Gunsight Pass) in which I nearly bought the farm and hurt a very nice piece of equipment. I was told it was water contamination, most likely a result of not topping off the tanks (I used to fly it home at night) and the condensation hanging from the tank ceiling vs dropping to the sump and being dumped in the preflight, could have been a factor.
Hope that helps,