The carbs are jetted super lean from the factory, the usual fix for this is to cut it open and stick a 110 main jet in there or replace with mikuni with 110 main and 30 pilot.
How fast were you going up the hill? They don't have a whole lot of oomph past 50mph or so.
Check out Motocheez's mods list for the hawk. He also has done a ton of youtube videos that show how to mod it:
https://sites.google.com/site/motoch...-250-resources
https://www.youtube.com/channel/UCfs...sZwINrc4KSbAlQ