Private Caboose Airsoft got this tutorial on how to replace the air hose of the Valken V12 HPA engine... "With the Valken V12 being discontinued, a lot of people are buying pre-owned engines.  For anyone who wants to refresh and renew the air line feeding into your V12 engine, here is an easy step by step guide.

This ensures that there are no leaks coming from an old and worn away hose, and that you are getting maximum air efficiency out of your set up."