Man I feel like an idiot! * http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/tounge.gif * Turns out I wasn't hooking up the carb properly. *I thought the hookup on the fuel pump part of the carb was a drain, i found out the hard way that is for the impulse line! *AAAAHHHHHH! * But good news is that the sled runs. *I got that "general snowmobiling" manual that goes through all the old sleds, carbs and motors, no where in there does it show how to hook up that carb. *When I got the sled the impulse line was disconnected so I figured that is how it has to be. *Oh well, it runs.

Couple questions: *Pistons have a front and back in this motor, what happens if one is put in backwards (1 piston was put in by someone else a while pback and probabbly didn't realize this)?

PTO side seams to be running leaner than mag side (one spark plug is light tan, one side is black), crank seal does not leak, what else could it be, could this be related to above question?

if the piston was put in backwards that cylinder would not run at all there are cut outs on the pistons that *line up with the ports in the cylinder if theywhere put in backwards the ports would never be open there for no fuel could get to that side glad to here you finely got her goin got any snow ride down here with some and we will go vintage skidoo riding 41degrees today and underdeveloped snow [rain]

mopar4u,
*atleast you didn't say you were just testing us all. *http://www.snowmobileworld.com/forums/iB_html/non-cgi/emoticons/sad.gif

mopar4u

Glad to hear you found the problem. At least you now have a spare carb and are an expert on Tillotson carbs.
P.S. the fix for vapor locking problem is to make the hole in the fuel return fitting on the carb a little bit bigger.