What kind of a shop changes a bunch of parts and but is unable to get bike to run? But I digress...
It's hard to diagnose anything with so little information provided. When is the last time the bike has ran? How long did it sit with old fuel?
If the bike will run with starter fluid, that means you have spark and timing is correct (or close). You likely have a fueling problem.
If you don't know how old the fuel is, start by emptying tank, flushing with fresh fuel and then refilling with fresh fuel.
Are you getting fuel from the tank to the carbs? Can you hear the fuel pump priming when you turn ignition on? Petcock working correctly?
If you can confirm you are getting fuel to the carbs, then I would pull out the carbs, dismantle and and clean them thoroughly (you should probably do this anyway). A carb rebuild kit (with new o-rings, needle jets, etc.) would be good to have, but not a necessity. If fuel has been sitting in the carbs for a few months, you will likely have varnish or junk in the carbs, stuck carb floats, etc.