MTD 550 Series Operator's Manual page 16

Service
7
FlexiblePumpCoupler
The flexible pump coupler is a nylon "spider" insert, located
between the pump and the engine shaft. Over time, the coupler
will harden and deteriorate. Replace the coupler if you detect
vibration or noise coming from the area between the engine and
the pump. If the coupler fails completely, you will experience a
loss of power.
NOTE: Never hit the engine shaft in any manner, as a blow will
cause permanent damage to the engine.
1. Remove three nuts that secure the pump to the coupling
shield. Two nuts are at the bottom corners and one is in the
top center. See Fig. 7-1.
Screw
Screw
Side-View Coupler
ge Lock Nut
Figure 74
2. Remove the pump.
3. Remove spark plug wire from spark plug and ground it to the
engine before pulling the starter rope.
4. Rotate the engine by slowly pulling the starter handle until
the engine coupling half set screw is visible. Loosen the set
screw using an allen wrench and slide coupling half off the
engine shaft.
5. Loosen the set screw on the pump coupling half and
remove the coupling half.
6. Slide the new engine coupling half onto the engine shaft
until the end of the shaft is flush with the inner portion of
the coupling half. (There must be space between the end
of the engine support bracket and coupling half). Tighten
the set screw.
7. Install the pump coupling half and key on the pump shaft.
Rotate the coupling half until the set screw faces the
opening in the shield. Do not tighten the set screw.
8. Install the nylon "spider" onto the engine coupling haiti
9.
10.
11.
Align the pump coupling half with the nylon "spider" by
rotating the engine using the starter handle. Slide the
coupling half into place while guiding the three mounting
bolts through the holes in the pump support bracket.
Secure with the nuts removed earlier.
Set .010" to .060" of clearance/gap between the nylon
"spider" and the engine coupling half by sliding a feeler
gauge or matchbook cover between the nylon "spider" and
the engine coupling half and moving the pump coupling
half as needed. Secure the pump coupling half with the set
screw. See Fig. 7-1.
NOTE: Make certain the proper clearance/gap is obtained
before tightening the set screw.
12. Reconnect the spark plug.
'°1