I am running a set of 34mm 220 special carbs on a V-4 Yamaha turning 6500 and below. The WOT runs good but 1/2 throttle plugs look a liitle lean. Can anyone help me fine tune these things . They have 4 jets in the front and two main fuel jets in the bowls. They are the old single float 220 special carbs . Thanks for any help. Joe R