I have a 300ex that I bought a used carb for. It won't idle at all with the choke off. With the choke on it idles perfect. I had a motorcycle carb on it but it didn't have a squirter on it and would hesitate when it was cold. The idle mixture screw does nothing. I've had this thing apart 20 times I bet and I'm stumped! I know right much about car carbs and have fooled with 4-wheeler carbs but this one takes the cake! The main jet and pilot jet is clear and clean. I've cleaned everything I know to clean but runs the same every time. Can anybody help?

 

I had this same problem. We just took apart the carb, thoroughly cleaned it and cleaned the jets. That solved our problem, hope this helps

 

hows the float?