So I let my father use my atv for a weekend. No biggy he has snowmobiles and takes care of them better than he took care of me
but when he put the atv away for the next 6 weeks he didn't shut the gas off.
Today I went to go use my bike and take it to my hunting land to clear out my deer trail from the tornado (worst 6 hours of straight chain sawing I've ever done) and the damn thing was running all goofy. I figured it was something with the carbs. Hard starting, sputtering, and I could tell through my Big Gun it was only hitting on one cylinder sometimes and both sometimes.
I went and grabbed a bottle of Sea Foam from ACE Hardware and dumped about 1/3 of it in the half full tank, filled it up with 93, and headed off to my land. Once I unloaded it, it was sputtering and occasionally you could hear it draw fuel and the rear cylinder would fire, but then choke out.
So I took it for a ride to warm her up and get the cleaner in there. Well I was driving about 15 mph at 1/3 throttle thinking holy crap I have major issues, then all of the sudden the quad backfired, hard, and I heard the second cylinder fire and that was the end of it. The Sea Foam cleared it up completely, the rest of the day it fired immediately and ran AWESOME.
So if you ever need a good system cleaner...SEA FOAM! White metal can, aluminum top with a white cap. I'm sure some other people can vouch for this product!