Tohatsu Carb - Low Speed Jet Cap

[teenuc]

I'm wondering what the rubber cap blocking the low speed jet is for? I'm sure the manufacturer did it for a reason (mixture, emission, drive-ability, etc.).

I've just started cleaning out a keihin carb on a 25hp Tohatsu motor, the rubber cap is degraded and am wondering what the results could be from not replacing it?

 

[pvanv]

It's for access to the jet (to change or clean it). The plug forces fuel to flow through the correct passages. Trying to run without it would make the mixture much too rich.