Welcome to the site !!
Has the bike been sitting ?? , and did this just start doing this , or has it been a ongoing issue ???
What is your current jetting and fuel screw set at , and your elevation ??
Have you verified that the squirt from the Accelerator Pump is just missing the slide and not hitting it ??
Are you using Premium Non Ethanol ?? , and is it FRESH ??
When it does run , does it stall easily ?? , does the Idle fluctuate ?? , and/or does it backfire when letting off the gas , or blubber/bog when giving it gas at any time while riding , and not when on the stand ??
Non Fuel Related:
Have you done any tests on the Ignition , coil, , etc. ??
How does the spark plug look ?? (color)
It could be a number of things , but with little background info aside from what you mentioned , we need to eliminate things to narrow it down ....