carb question

[U.P.'er J-20]

i completely gutted the emisions out of my j-20 along with the choke plates and linkage from the carb and i noticed a smaller butterly type plate in the back of the carb so i removed that too. i was wondering what is that for i also noticed when i removed the top plate of the carb to change jets that below that smaller butterfly there is sometype of spring loaded apperatice and two ports going under the main throttle plates that seems would open up and allow more air into the engine under a certain situation does anyone what thats for after i changed jets it fired right up and seem to run great i redlined it a few times and didnt miss a beat i just havent run it on the highway yet since my front end is still torn apart, i just dont want any surprises once i get everything together because i plan on going wheeling for the first time this year

[Bob Barry]

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^^^
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You might want to scatter a few of these around next time... ;)

AS for your question. What you describe is the altitude compensator. It keeps the carb from running too rich at altitude by allowing more air past the throttle-plates. Don't screw with it; it's not really user-adjustable and it won't improve performance if you try to modify it.

But you don't need a choke to get that beast going in cold weather?