My uncle has a Yamaha 50 2 stroke. Not sure what year but it is close to 2004. It will not start. It will start and run if he shoots starting fluid in ( I have heard that is not good so I told him to stop).
Thinking it is some type of fuel issue. We disconnected the fuel lines to the tank and and tried feeding directly from a gas can. No joy.
I can pump the primer ball and it gets hard.
I disconnected the fuel line after the fuel pump (part number 30 in the pic below) and pump the ball. Fuel shoots out of the fuel pump. If we turn the engine over with the line off fuel barely sputters out. I figured that fuel should be shooting out of the pump when we turn over the engine, is that right? If so does that mean that the fuel pump is bad? If so do you figure replacing the entire fuel pump at about $40 or just the diaphragm for $10?
You said it starts and runs with the starting fluid. Does it keep running or die after the starting fluid is gone. Also it should start even with a bad fuel pump. It shoud start and run untill the carb bowl is empty and then die. It sounds to me like it needs a good carb cleaning.