Maybe a carb rebuild kit will have it? Just a long shot. Would be worth looking into, anything's better than buying a new carb or an old one needing a rebuild.. $$$
Try this diagram, breaks down the carb part by part. Hope it helps
http://www.cheapcycleparts.com/model_years/4789-yamaha-2002-warrior-yfm350xp/assemblies/140893-carburetor
If it doesn't take you there you'll have to put in your make/model/year.