Manual

Maintenance and Service 35
d. Carefully install the air piston into the piston insertion tool so that the entire air piston is
completely inside piston insertion tool.
e. Ensure that the air piston is installed without any gaps or folds and is evenly round.

NOTE If the installation is unsuccessful and the air piston was damaged in the process,
replace air piston and repeat above steps. If not, continue with next step.
f. Turn the piston insertion tool upside down so that the air piston is facing down towards flat
clean surface.
g. Using the o-ring lubricant, lubricate the o-ring and install the o-ring in the groove of the
chamfered end of the seal lock nut.
h. Apply pressure to the seal lock nut while installing it in the top of the piston insertion tool and
into the air piston for a secure installation.
2. Using the o-ring lubricant, lubricate the threads of the needle.
3. Install the air piston to the needle as follows:
a. Place the piston insertion tool on the top of the needle.
b. Start turning the piston insertion tool clockwise a few turns to engage the needle threads.
c. Thread the seal lock nut onto the needle until the lip of the piston insertion tool seats in the
chamber on top of the upper body.
d. Continue to turn the piston insertion tool until it disengages from the seal lock nut.
 At this point, the top of the seal lock nut should be within 0.46-mm to 0.51-mm (0.018-
inch to 0.020) above the top of the upper body.
e. Using the piston height gauge tool, place the notched edge across the seal lock nut so that
the feet of the piston height gauge tool rest on the upper body surface.
 No gap shall be visible under the notched feet or notch. If necessary, correct air piston
installation by repeating Step 3.
4. Gently pull up on the needle approximately 1/8–inch but do not pull the air piston out of the air
piston insertion tool.

NOTE Air piston adjustment is often necessary when you replace the upper body u-cup
seal or the needle. In these cases, follow the disassembly and reassembly
instructions in this section, but do not actually replace the air piston unless it is
damaged. Improper air piston adjustment may result in poor dot quality (dots not
breaking off from nozzle).
5. Place the spring retainer on the needle.
6. Using the module-adjusting wrenches, hold the seal lock nut in place and tighten the spring
retainer for a secure tight installation.
CAUTION! To prevent damage to the needle, do not over-tighten the spring retainer.
7. To properly seat the needle, ensure that the top of the seal lock nut is flush to above the top of
the upper body.