Hey OPT, I have recently rebuilt the carb and notice that at higher RPMs the carb starts to drip a bit of fuel. I've used a 1/4 inch clear drip line to verify my fuel float level is set correctly and fuel line stops at the carb bowl seal at idle. I've heard these models commonly have this problem. Is there any possible way to stop it? It leaks about a half soda capful of fuel in 15 mins. Thanks.

 

BST40 is a funky carb in the way the bowl itself holds the float assembly and needle valve down. Hard to set it using a clear tube as you would a normal carb. Float has to be set just right to keep from leaking. Had a few that still dribbled just a tad while at an idle no matter what I set the float at.On these I just ran a longer length of drain tube to extend beyond the bash plate and not on the engine. Plus one other thing to check is to make sure the o-ring around the needle valve seals tight when you lightly push on it with your thumb. Could be that some aftermarket kit o-rings are a little different and cause some of the problem if fuel seeps by the o-ring? Read this article on the BST40.Similar carb but used on a Ktm.Goes into detail on float setting.The BST-40 Bible | Adventure Rider