Does the choke circuit on your bike fully work - and make any difference ??
Many bikes simply will not start cold without choke.
The FIRST major thing to look at with starting difficulties is the spark plugs.
They should be cleaned, and gapped to the correct gap.
And if that doesn't help, try one ones.
Along with cleaned (or new) air cleaners, and fresh oil in the engine (if its about due for a change).
And correctly gapped and set points for the ignition (if it doesn't have electronic ignition, don't know XJ550 that well).
Along with wiping clean all the spark plug leads, around the coil and wiring etc.
Carbs all synched and idling well when warm ?
Fresh gas in the tank - old fuel seems to evaporate all the lighter fractions- that make it easy to start.
If it STILL doesn't start, try reducing the gap on the sparkplugs, not by much ( a few thou).
If that works, as a last resort, consult back here.
P.S. Happy New Years all.
