The Mikuni carb on my 2002 LT-A50 has a needle valve with no spring. I'm used to seeing springs on the needle that keep it away from the seat, and the float then presses against the spring tension to close the valve when the fuel level gets high enough in the bowl.

On this Mikuni BST 34, there is no spring - which means the valve operates entirely by gravity! It just rests against the tab on the float. It seems to work, but I've never seen another one without a spring.

The exploded diagrams of the carb only show the needle and seat as a complete assembly. They don't even show the needle being removed from the seat. Thus I can't tell from the illustrations if there's supposed to be a spring in there or not.

Anyone else clean one of these carbs and notice if there's a spring in there?

 

no spring on my 400 it just uses gravity and the float also