Off-Idle Hesitation

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Wizard....your carb issues sound exactly what I went through with my 418W last week. I pulled the plugs to change them and they were very sooty. This is because I was idling too much off the transfer circuit and not the idle circuit. I initially had both the primary and secondary throttle blades opened for a balanced idle on all 4 corners. What I did next was reduce the idle speed by turning down the idle speed screw on the secondaries so it was barely open. I turned my idle speed on the primaries down also to an idle speed of 900 rpm. This seems to be the lowest idle rpm that my motor is happy at. Next I turned in the mixtures screws, increasing the idle speed. Then I again turned the primary idle speed screw back down to return engine speed to 900 rpm. What this did was allow me to adjust the throttle blades away from the transfer slot and closer to the idle port. I expect the idle mixture will be cleaner at this point. If you turn in your mixtures screws and there is no change in idle speed, guaranteed you are working off the very rich transition circuit and not the idle circuit. This makes for a very dirty idle mixture. As said before, if this fails you may need to drill some small holes in the throttle blades to allow more air into the motor withouit opening the throttle blades into the transfer slots. Just start at drilling a 1/16" hole first. I'm sure your motor is just as fussy as mine trying to get this idle mixture and off idle stumble as clean as possible.

Bill