Hi there

What is the orginal needle size and needle seat (q?) in T-cat 2000, flatslide?

The reason I ask, I wanna richen my midrange a litle, before I install ATACC.

Someone did mention 50 pilot and q5 seat for t-cat 99, make any sens a rich midrange setup for flatslide 2000?

What a about needle pos with 50 pilot and q5?

I run 350 mains, plugs looks ok, but clutch one is a litle light for me, so I will probabilly run 370 on that one and perhaps richer middle range also.

Any idea? Stock number?

Well all I can help you with is the stock Jet needle and it is a 9DFH03-56 and the part number is 6506-186. If you are running stock jetting and intake on your T-cat they come pretty rich straight from the factory.Look Here (http://www.brownsleisureworld.com/Parts/SNOWMOBILE/2000/2000THUNDERCATGREEN(S2000TCLAAUSG-2000)/CARBURETOR-INTERNALPARTS.htm)

If your jetting was good before, you should only need to change the main jet for the target temp. There should be no need to change the needle jet or jet needle if the compensator is the only modification you are making.

I agree with 94ZR just change the main jet size. My ATACC works awesome with just changing the main jets to ummmmm I don't remember the exact size but whatever brought it down to -20 setting. This year I should have gone to -40 with these temps out here!!!