8706012 3.9 Gallon Backpack Sprayer V4.0
8 For technical questions call 1-800-665-8685
6. Check for vertical scratches on the inside
of the piston cylinder (#28), the piston (#28)
and the collar (#30). Replace any part with
scratches (Fig. 5).
7. Push the collar off the piston’s crown with
your thumbs when replacing it. Detach the
internal compression spring (#29) in the
collar. After replacing the collar, re-attach
the spring to the collar (Fig. 6).
8. There are 2 valve plates (#27) on the piston
cylinder, one on the inside of the cylinder and
one on the outside top. The valve plates are
held in place with a Phillips head screw (#25)
and a flat washer (#26). Check and adjust if
necessary (Fig. 7).
9. Check the o-rings (#22 and #24) for damage
and ensure they are positioned in the o-ring
grooves on the piston cylinder (Fig. 8).
a. Grease the o-rings on the piston cylinder
(do not get any grease on the valve plates).
b. Screw the piston assembly into the
pressure cylinder base. Screw the piston
clockwise until tight and the bottom o-
ring is no longer visible.
c. The tab (#B) on the piston cylinder will
line up with the rib on the pressure
cylinder base when properly placed.
10. Apply petroleum jelly to the inside of the piston
cylinder wall and on the collar, and reinstall the
piston assembly into the piston cylinder (Fig. 9).
11. Insert the piston at an angle with the leading edge
of the collar placed over the slot in the piston
cylinder. Bolt the piston assembly to the pump
shaft using socket hexagon screw (Fig. 10).
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
