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78/83/90 Series Horizontal Shaft Engines
100
Cylinder head installation
1. Place a new head gasket on the cylinder, allowing
the alignment dowels to hold it in place.
See Figure 9.8.
NOTE: MTD uses graphite head gaskets that have
a bead of silicon on them. They are not reus
-
able.
2. Position the cylinder head on the engine block.
3. Install the 4 head bolts, and tighten them to a step
torque of 38 - 41 ft-lb. (52 - 55 Nm) in an alternating
diagonal pattern.
See Figure 9.9.
NOTE: The bolt closest to the exhaust valve must
be the last bolt tightened. Failure to do so
will result in the head bolt loosening up.
NOTE: The 490 engine has an over sized bolt with
a Belleville washer in the number 4 position.
4. Insert the push rods.
5. Install the rocker arms.
6. Adjust the valve lash by following the steps
described in Chapter 1: Introduction.
7. Install the throttle lever and the heat baffle.
8. Install the muffler by following the steps described in Chapter 8: Exhaust.
9. Install the carburetor and engine shroud, using new gaskets, by following the steps described in Chapter 3: Air
Intake
10. Test run the equipment in a safe area before returning it to service. Check all safety features.
Figure 9.8
Graphite head
gasket
Figure 9.9
3
Exhaust
port
1
2
3
4
For Parts Call 606-678-9623 or 606-561-4983
www.mymowerparts.com