Run a search for "reed block mod" and it will come up right here on RCU. This is VERY common on the Chinese reed induction engines. All you do is pull the carb, then reed block out of the crank case. Remove the reeds, then place some fine sandpaper on something really flat like a piece of glass. Make a few passes over the faces of the block and that will remove any burrs or high spots that are causing the reeds to not fully seat. Then when you reinstall the reeds put a drop of locktite on the screws, and turn the reeds over so they put the most closing pressure on the block before installing the screws. Usually if you have leaky reeds the engine might be slightly hard to start, and not want to idle perfectly well. You can still get some spit back through the carb even with properly working reeds, usually at high rpms with the reeds begin to float or hang open a bit. Lots of guy install a Bowman ring AND do the reed block mod at the same time and say they have never run better.