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78/83/90 Series Horizontal Shaft Engines
102
4. Lift the springs off of the valve stems.
5. Slide the valves out of the cylinder head.
NOTE: Only the intake valve has a valve guide seal.
See Figure 9.12.
6. Inspect the valve seat. See Figure 9.13.
• Valve seats are 45 degrees, with a 31 degree
topping cut and a 61 degree narrowing cut.
• Seat width should be 0.028” - 0.035” (0.7 -
0.9mm) with a margin of 0.024” (0.6mm) on the
exhaust valve and 0.027” (0.7mm) on the intake
valve.
NOTE: The valve seat can be ground to clean it up
as long as the finished seat is within the tol
-
erances listed above.
7. Inspect the valve stem. See Figure 9.14.
8. Inspect the valve springs.
NOTE: Valve spring free length should be at least
1.22” (28.5mm). Original length is 1.44”
(36.6mm).
9. Install the valves in the cylinder head by following
steps 2 - 5 in reverse order.
Figure 9.12
Seal
Figure 9.13
Seat angle is 45
o
0.028 - 0.035”
Seat
contact
margin
Figure 9.14
45
o
Inspect for a
burnt edge
For Parts Call 606-678-9623 or 606-561-4983
www.mymowerparts.com