I know this post is old, but if you ONLY did an oil change and wash job there should be no water in your carb. thats alot of water to fill the exhaust all the way back to the carb,(and past five valves!) You got some water....might be very little... on the spark plug boot(down at the plug), it only takes a little moisture to get a misfire. remember the spark will always go to the place with least resistance. It's quite possible and not un-common to get water into your intake, in the air box and through the filter during an agressive wash. We weren't talking or referring to getting water in the carb through the exhaust opening on the can/muffler. The OP started the thread 2 weeks ago, and is still trying to find a solution to his problem.