Yep, you've either got a float that is sticking, and or need a float valve repair kit. Read this thread and let us know how you fare. https://tw200forum.com/index.php?/top...__1#entry16338
You can probably do it, but if you are a total nubie with carbs, I'd suggest a friend help or you invest $50 to have it done by a professional. IMHO. Good luck. Tom
Oh, in the meantime always turn off that petcock when you are not on your bike. When the engine is running it will probably consume enough fuel to keep up with the leak. T.