3 things you always must have..compression,spark and fuel..
So..if you can access a compression gauge,check compression.
Pull all the plugs out and make sure none are fouled..put the plugs in the spark plug caps and lay them on the engine,then spin the engine over to make sure all four are sparking properly.Ive seen bad plug caps which had so much resistance a bike would barely run...also,check to make sure the wires that slide over the little spade connectors on the coils are hooked up,im cant remember the colors but there is a positive+ and a negative-....you should show 12v+(or battery voltage) at the positive connector with the ignition switch turned on..
Make sure the plug wires are on the correct cylinder...if you are looking down on the bike from overhead,the coil on the left has the wires for #1 cyl and #4 Cyl...the coil on the right is #2 and #3...(ive seen plug wires going to the wrong cylinder,makes a lovely backfire with cool flames coming out exhaust.)
You say you have fuel...just to make sure,crack the drain screw on the bottom of each float bowl to make sure theres really fuel in all 4 carburetors..
Are you using the choke when you try to crank it?If so,dont move the throttle just hit the starter button and let it turn over that way..If the choke circuit is working correctly it should run.
Has the bike been down on the right side?Is the ignition cover intact and not broken?Just making sure the pickups under that cover are in ok shape..dont want them rubbing...im pretty sure theres no adjustment but you might want to pop that timing cover off and have a look.Also,theres the *CDI box* that the wires from the pickups go into..but usually when one of those goes bad(which isnt often at all) you will have either no fire at all or maybe just fire on one coil instead of them both..
So assuming the timing is correct,theres engine compression,and fuel,it should run.
Check that out and let me know
Joe