ran fine last year, now won't start

Living in Vermont, I thought I was going to be able to ride a lot more last year. Then all of a sudden it was winter and I hadn't properly winterized. I had just done an oil change so I wasn't that worried about that. I was also in the habit of fueling up at the marina gas station that still had ethanol-free gas. Anyways the bike was running nice last year, and now it won't start.
This year I ended up yanking off the carbs and draining all the gas in the tank in case it was bad. I checked the oil and made sure the level was right. I had the battery on a tender all winter. I had an in line fuel filter and I replaced that while I was at it, and put on some new fuel line since the old one was a little short. I cleaned the carbs with a spray carb cleaner and blew them out with an air hose. I reassembled everything, and put in some new gas that I added sta-bil to. When I tried to start it, it tries but doesn't fire up. It sounds like it is about to, but just doesn't get all the way there. The starter is going chug chug chug and you can hear a faint pop pop pop but it just won't start. After a few tries I attached a battery jumper box for a little extra oomph but it still wouldn't start.
Should I assume that I didn't get all the fuel residue out of the carbs and rip them off and try to clean better? I read up on forums for similar problems and solutions and someone suggested soaking the carbs in simplegreen for a thorough cleaning. Anyone have any ideas on what I should do next?

If the fuel system had gas in it without stabilizer, it probably turned to varnish and choked up the passages inside the carbs. The jets and passages have to be properly cleaned. You can TRY draining the carbs then filling them with chemtool, gumout or some strong concentrated cleaner going in the gas inlet tubes. let them soak a few days, then drain and rinse. Repeat as necessary. You can also "hose down" into the fuel inlets using carb spray. This might eventually clear them but they may still need to be disassembled and cleaned. You also need to clean the fuel tank and petcock assembly.

From what you described and the steps you took to insure that the winter wouldnt have any harsh effects on it.

I have to say it sounds like an electrical problem, rather than a fuel problem. But I am not an expert. If it is clogged fuel lines, just try to flood it. A really easy way to check for spark is to take a screw driver, put it in the boot, hold it next to an engine bolt and see if it archs a spark.

just an update. I checked the spark to rule it out. I pulled the plugs, they were all black and sooty and on top of that wet with gas. I cleaned them all off, checked the gaps, and checked for spark and they had good spark. So, I yanked the carbs off again and on my friend's recommendation I took out and cleaned the air/fuel mixture screws and springs and the passages. I made sure to check how many turns it took to tighten them all the way before I took them out. When I got them out I realized there was a bunch of shmegma in the passages and on the screw needles. I cleaned it all out with carb cleaner and reassembled. After that it took a few tries but then it fired right up.