What is the purpose of the 6 check valves on the intake? (They don?t come with the carb kits do they?) I pulled my carburetors last night for rebuilding and I am considering replacing the check valves as well (or can I just remove and clean them?). She?s been very hesitant on start ups and especially after running under load at low rpm?s. At low rpm?s I can hear it just bog out, then I have to goose the throttle in neutral to get it to go again. She also started spitting back after start up the last time I took her out. I know the carbs need work but I am uncertain about whether I should do anything with the check valve as well while I have it apart.