Hi this is my first time on this forum. I have an 1981 ET250 single cylinder. Is anyone extremely familar with the carb that is on these sleds? It has no float or bowl. It has a fuel pump built into the carb. The problem is I can't make the thing run. It will run if gas is sprayed down it's thoat. The carb is getting fuel, the carb has been kitted. The needle valve is free the passages are clean. BUT in the main part of the carb, Right in the very center, only to be seen when carb is apart, there is a little plug (car mechanics would call it a limiter cap, and it also looks like a tiny frost plug). This plug is rusty and I need to know what is behind it. It seems to line up with the brass venturi in the thoat of the carb. What is under that cap? and if it is dirty under there would it prevent the snowmobile from running???