High and Low speed mixture screws are blocked off on your ski. This was an EPA compliance thing.
You need pull the carbs off and removed the brass plugs. The plugs can be removed in many different ways. The stock mixture screws have a very shallow screw slot that will be easily damaged when drilling out the brass plugs. I purchased T-handle mixture screws to replace the stock ones.
Best method I found for removing the brass plugs was to cut off the extended boss holding the plugs. I drilled the first one out and found the boss was to tall to allow the T- handle to fully close. I measured the depth of the brass plug and cut the remaining three off with a hacksaw blade.