Sun Pumps AP-SDS User Manual
Page 3
SDS PUMP REBUILD INSTRUCTIONS
ASSEMBLY
1. Set the two pistons (Items 11) flat side down on the pump assembly plate, positioning
the two holes over locating studs.
2. Place the diaphragm (Item 12), with the offsets up, over the pistons locating the piston
shafts through the two holes.
3. Slip the outer pistons (Item 13) over the piston shafts with the radius side toward the
diaphragm.
4. Set the motor adapter (Item 14) face down over the diaphragm assembly allowing the
piston to protrude through the two holes being careful not to nick or cut the diaphragm.
5. Put the set screw into the cam and insert the cam assembly (Item 15) over the piston
shaft making sure the piston shafts fit into the cam plate holes.
6. Insert the two washers (Item 3) and two piston screws (Item 23) through the cam
assembly, and tighten with a 5/32" hex wrench to 60 inch lbs. of torque. (Be careful not to
allow the pistons to slip off the locating studs while tightening the screws.) Each screw
should be tightened a little at a time alternating between each side. This will pull both
pistons into alignment before either piston clamps the diaphragm.
7. Place the motor on the assembly board with the shaft up. Turn the motor shafts until
the flat side faces you.
8. Coat the inside of the cam hole and the outside of the motor shaft with silver anti-seize
compound.
9. Insert a long 1/8" hex wrench through the hole in the motor adapter and into the cam
set screw.
10. Slip the cam assembly over the motor shaft aligning the set screw to the center of the
flat on the shaft. As the cam assembly is inserted over the motor shaft tighten the set
screw until it lightly touches the motor shaft and then back it off 1/8 turn. Continue
installing the cam assembly until the motor adapter butts up to the motor. Then push on
the pistons until the cam assembly bottoms on the motor shaft. While holding the piston
down firmly, tighten the set screw.
11. With the motor assembly still on the board, gently lift the diaphragm up on each end
and insert one stainless washer (Item 3) in each motor adapter hole.