I've got a 05 Yamaha bruin 4x4 A/T but very similar looking carb setup. And VERY similar problems when I let it sit for an extended period of time. My issue was the carb, took multiple attempts of cleaning, spraying, soaking before I got it to perfect working condition. The brass philips head screw sticking out in one of the pics can slightly adjust your throttle. Mine took a fine tune of that when it was all said and done. Also, is your choke working correctly?? Things to remember with these; be very careful with the rubber gaskets, as they can warp and leak easily when dis/reassembling them, also not a must but I found in mine that the stock fuel filter in the tank is garbage, it was dried and cracked and surely causing more harm than good to my fuel, easy fix is to unscrew the petcock from the tank, check/remove if needed, and add an inline fuel filter on the line between your tank and carb. 
Any questions, feel free to ask.
Broke down and took this thing to a friends house to work on it, since he knows what the hell he is doing and I don't. I just couldn't keep it running, and since my lease is so wet I am going to need it. I had intentions of getting a golf cart, but that is on hold for now due to the water..
He was into it about 10 minutes, and found about three things wrong with it. Parts are already on order and should be slapped back together as soon as they come in. Its good to have friends that know what they are doing and save you money having to take crap to a dealership or shop...
So what went bad???
