Piston valve repair kit 287837 replaces the piston valve in displacement pump 287834, the lower inside the RPS 2900 pump fitted to RoadLazer RoadPak and RoadPak HD line striping systems. The piston valve is the check at the bottom of the piston rod, and it is what lets the pump build pressure on the down stroke.

A worn piston valve shows up as a pump that will not hold on one stroke. If the pump holds going down but drops going up, or the other way round, the fault is in one of the two valves rather than in the packings. Traffic paint is abrasive and the piston valve wears alongside the intake seat, so it is worth having both on the shelf ahead of a marking season.

Supplied as Graco's complete piston valve kit. The 22.2 mm piston ball that runs against it is not in this kit, it comes in packing kit 287835. Position and rebuild procedure are in manual 311485 below, reference 210.