Snowmobile Repair: 1991 Wildcat, air jet, fuel system

Question
my cat will start and sit and itle all day long.
I can take it out for a 5 min ride and all is good. BUT if i take it out for a long ride as soon as it gets hot it will have no power and smoke like heck. I can hardley get it to move. but if I lift the hood as I go it will run better, but not great. It acts like the plugs are bad. but if put new plugs in it will be the same. As soon as it sits for a good langth of time it will work great. Till it get hot.
I have 120 psi in both it is ported and i have boyesen reads in it with the stock stopers in it.
I have went thuw the wiers, (good) the carb is (I think) set right. the needle is on the 2 clip down, air jet is 1 1/2 out. it sound like it is fooding out? I see a littal gas in the air box.
so i need help i dont know if it is the carb or if it is not fireing right (CDI) or (COIL) when it is hot.
Help!!!
Gary

Answer
Hello Garry,

 You are right, it is flooding. It could be the carburetor, or it could be a problem with the ignition system not operating properly. Here is what I would recommend. First, try cleaning the carb thoroughly, and possibly install new jets. The correct jets for the sled are 400 for a MAIN jet and 50 for a PILOT. When cleaning the carb, something to pay special attention to is the inlet needles. They are very prone to sticking. It would be very wise to install a new carb kit. You can get them from www.denniskirk.com or www.mfgsupply.com for a reasonable price. For a reference, the carbs on the sled are Mikuni VM 40's. If after checking the entire fuel system over for faults, I would suspect the coil. Hope this helps. Let me know if you have any other questions. Good luck with the Cat! --Arcticatman