Join Date: Nov 2014
Location: North Central Indiana
As discussed repeatedly in "bayou 300 carb problems", there are many problems that can develop and as you said in the first post, can drive a person "mad." A lot of these discussions center around the float needle and needle seat which is not replaceable on these. A lot of people have experienced overflow problems which can be very dangerous. Yours may be sticking and allowing fuel flow, and then not allowing it. Take a Q tip and use toothpaste or any fine polishing compound and polish where the float needle seats. I use tiny dab of valve compound but just about anything similar will work. Then make sure you clean and get it ALL out of the carb. By polishing it, it 'should' work but sometimes it just doesn't and the carb has to be replaced.
The fuel level should be + - .5 to 1 mm above the bottom edge of the carb body- meaning the top of the fuel bowl. While the factory service manual calls for a special tool, you can easily use a piece of clear tubing connected to the fuel overflow. Hold the tubing above the fuel bowl and then open the fuel drain on the bottom of the bowl and open the petcock. Gravity will show the fuel level by filling the clear tube. Don't let the top of the tube drop below the bowl and carb body or it will give a false level.
It could be that the float itself has a pinhole, but does not sound likely in your case.
The way these carbs are designed to operate is totally different than what most people are used to. The mixture screw is a pilot jet, fuel only, and has nothing to do with air mixture. The service manual calls for 2 1/8 turns out from lightly seated. There are after market replacements which help to keep you from burning your hand trying to adjust it.
The choke is really a fuel enricher for starting purposes when necessary. It should not be necessary when its warm out.
Also, when working on these carbs never allow fuel to reach the rubber diaphragm in the upper half. They want an arm, leg, and first born son to replace it. The diaphragm depends on differences in atmospheric air pressures to operate the slide. While all carbs work that way, this design is very different. As I stated in other posts, I'm "not the first person to take a mirror and watch the slide flutter" and struggle to work like it should.
I bought a 1986, and then a 1988 for "parts." Now I ride both of them. I eliminated the carbs and found a way to enjoy riding instead of constantly messing with a carb or finding myself stuck out in the woods. In my opinion, a factory service manual is a necessity for working on just about anything. They can be found on the web for a few bucks to download. Well worth it, but still are not 'gospel." (Holy Kow) Good luck. Wish you were in central Indiana so I could have a look.