1998-2000 Yamaha WaveRunner GP800 Factory Service Manual, Page 68Get this manual
!FUEL!_ SERVICE POINTS
Check valve inspection 1Check: Check valve Faulty ReplaceChecking steps: Connect hose to the end of check valve "Au and blow into itAir should come out from end "8" Connect the hose to the end of check valve "8" and blow into itAir should not come out from end "AU