Snowmobile Repair: wont idle, engine seals, air screw

Question
I have a 91 Articat Lynx 300 for my wife.
The problem is that the engine will not idle. I have pulled the carb off and cleaned it but it still will not idle. The sled will run at higher rpms. If I give the sled a quick choke it will idle for a few seconds then try to quit.
Could this be the fuel lines? Last year, the sled had a sporatic idle. (not very smooth)
Any suggestions,
Thanks.  

Answer
Hello Vinnie,

  It could be a number problems causing the stall at idle speed. I'd start with the pilot jet(s). Check to make sure there isn't gum built up inside of the them, it can cause a hard idle problem, and is fairly common. I don't think you have an ignition problem, unless your spark plugs are fouling, I would recommend looking at them to see if they are getting fouled. The fuel lines would be something to check into, but more important would be changing your fuel filter, if the sled is equipped with one. I'd tend to think it may be more of a jetting/mixture related issue, though. Also, a slight  air leak is a possibility also. It sounds like the idle speed is too low and the lean condition lets the idle speed hang for the few seconds it does idle, with the help of the choke, before it dies. The first thing I would do is try adjusting the air screw. It may be as simple as richening the air screw. If that doesn't change the idle, check for an air leak by spraying some carb cleaner around all the engine seals and gaskets while it is running. The seals are located on each end of the crankshaft, but the only one you will be able to spray in the clutch end. If you get a change in rpm, that would indicate an air leak. Another thing to do is to try adjusting the idle speed. It is the large screw on the side if the carb that sticks straight out, with a visible spring on it. Hope this helps you out, let me know if I can answer any other questions you might have! Good luck with the Cat! --Arcticatman