MTD P61 Series User Manual

Chapter 1: INTRODUCTION
8
6. Confirm that the piston is at T
op-Dead-Center on
the compression stroke. See Figure 1.10.
• The compression stroke can be distinguished
from the overlap stroke by the presence of air
pressure at the spark plug hole and the fact that
neither of the valves should move significantly
on the compression stroke.
• There is an automatic compression release
mechanism that “bumps” the exhaust valve as
the piston rises on the compression stroke. At
TDC, the exhaust valve should be fully closed.
7. Check valve lash between each valve stem and
rocker arm using a feeler gauge.
8. Intake valve lash (top valve) should be .003”-
.005” (.10 +
.02mm). See Figure 1.11.
9. Exhaust valve lash (bottom valve) should be
.005-.007” (.15 +
.02mm). See Figure 1.12.
10. Use a 10mm wrench to loosen the jam nut, and
a 14mm wrench to adjust the rocker arm fulcrum
nut. See Figure 1.12.
• Tighten the rocker arm fulcrum nut to close-up
the clearance between the end of the valve stem
and the contact point on the rocker arm.
• Loosen the rocker arm fulcrum nut to open-up
the clearance between the end of the valve stem
and the contact point on the rocker arm.
11. Hold the fulcrum nut with a 14mm wrench,
tighten the jam nut to a torque of 88.5 in-lb.
(10Nm) using a 10mm wrench.
12. Double-check the clearance after tightening the
jam nut, to confirm that it did not shift. Re-adjust
if necessary.
13. Rotate the engine through several compression
cycles:
• Observe the movement of the valve gear.
• Return the piston to TDC compression stroke
and re-check the valve lash to confirm consistent
movement of the valve gear, including the slight
bump to the exhaust valve from the automatic
compression release.
14. Clean-up any oil around the valve cover open-
ing, clean the valve cover, replace the valve
cover gasket if necessary.
15. Install the valve cover, tightening the valve cover
screws to a torque of 71 in-lbs (8 Nm).
IMPORTANT: Over tightening the valve cover
will cause it to leak.
Figure 1.10
Valves closed
(push rods slack)
Probe to confirm piston
is at top of travel
Figure 1.11
Setting intake valve lash
.004” feeler
gauge
Figure 1.12
S
e
tti
ng ex
h
aus
t
va
l
ve
l
as
h
.006” feeler
gauge
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MTD P61 Series Specifications

General

Brand	MTD
Model	P61 Series
Category	Engine
Language	English