fuel starvation on a carb Yamaha

[jwiii]

I had a similar problem on a 98 SW 200. Listen to the guy who said to replace the primer bulb. It fixed mine.

 

[goinsfishin]

Assuming the water/fuel separator is clean (if you have one), the next steps are primer bulb, fuel filter on engine, fuel pumps, then carbs.
An easy check of fuel system is to get an auxilary tank and run the engine off it. If the motor runs correctly on the aux tank it's a fuel delivery problem, if it still runs poorly it's on the engine side.
Look closely at the fuel pumps, replace if more than a few y/o...a pinhole in a diaphram can cause all kinds of bizarre problems.