Another Day another problem

[Monkey Butler]

Sounds like you need to go through your carburetors and clean them out.

For just off idle to mid range there are a few tiny drilled passages that admit fuel to the engine, they are located in the carb bore so that they are exposed to vacuum one by one as the butterfies open up.

I'm guessing that you have a few clogged but once you get into the main jets things smooth out. They all add to the total fuel flow though so you are probably running lean at higher RPM's. The nice thing about Yamaha's oil system is that it adds oil independent of fuel so you won't be down on oil but lean is only good up to a point in 2-strokes.