bogging out

Hello everyone. I have a 77 kz900 just recently rebuilt and when i start her up cold she on full choke runs fine after about 2 mins she bogs down. to me it seems like she is flooding out so i took my carbs apart and cleaned. Put them back together ran great for about 20miles then as i was going up hill and more throttle she bog down. any advice thanks.

Any mods to the airbox/petcock/lines etc?

Have you taken your petcock out and/or cleaned your tank out. Was there much sediment in your carb bowls when you took them apart? You may want to try an in-line filter.