2001 monster 600 wont start

[recklesskelly]

I've rebuilt the fuel pump, checked the fuel
lines. put in new properly gaped spark plugs and check the starter and
fuel filter. The battery stays on a battery tender so it's always
fully charged. Everything works fine it just cranks sputters and
stalls. leaving me scratching my head wondering why it will not turn
all the way over and stay started.

any advise would be well appreciated.

[zooom]

when was the last time it ran? have you tried spraying some starter fluid into the throats of the carbs for to aid in starting or anything like that?

[Howie]

How old is the fuel?  Are the plugs wet (engine flooded)?  Careful with the starter fluid, that stuff has an octane rating approaching 0.