Yorbie: Episode One

Once you've upgraded a weapon fully (3 upgrades), you can go back to an upgrade station and choose to reset the weapons stats. Doing so will remove all upgrades from the weapon, so you will have to reapply the upgrades if you want to keep using the weapon at full proficiency.

Enter an upgrade station, choose the weapon you wish to reset, and hit to sell the upgrades. You will earn back half of the cogs you spent on the upgrades after doing so.