Check your O-rings on the needle/seat assy.I had two dried up,small and leaky ones that stumped me years ago.Do this before you lean your jetting.Clean those carbs,turn them upside down, and pull on fuel inlet like a straw, using your mouth and then cap it with your tongue.You'll tell right away if leaky, as it wont hold vacuum.If there good ,it might give your tongue a little hickie,hahaha,honestly.Anybody else notice how stale gas really stings taste buds? hahahaha.O-ring can be had at local NAPA store for cheap.