Believe it or not, that can be a $5 fix with oem parts if your description is correct and my diagnosis is as well. From what I read, you should give my advice a try.
If your buddy likes to buy cheap fuel with ethanol, and the atv sits for extended periods, I may be directly responsible for saving you and your friend some serious cash. Little known to most Yamaha atv owners with carbs, and this was(is) dealer/tech info, that if you can only find from those privy to the info, that all you need is a couple of o rings replaced on the nozzle portion of that pumper carb to make it behave like new.
You wont be able to duplicate these unless you have a custom o-ring dealer at hand, but your looking for Yamaha part# 93210-10118. Dont cross check that part number for fitment as it comes up for many models over many years and none apply to the carbs. Trust that I have been in your situation and have some inside knowledge.
By the way, there is no "western", its either north or south. Where you at?