3to 11hp 4-cycle l-head engines - Small Engine Suppliers

CYLINDER HEADS
8
4
6
Check the cylinder head for warpage by placing the head
on a precision flat surface. If warped in excess of .005"
(.13 mm) replace the head. Slight warpage can be
corrected by placing a sheet of #400 wet /dry sandpaper
on a precision flat surface and rubbing the head gasket
surface in a circular pattern until the entire gasket surface
shows evidence of sanding. A small amount of honing oil
on the sandpaper will make it easier to slide the head.
Always replace the head gasket and torque the head bolts
in 50 inch pound increments in the numbered sequence
to 200 inch pounds (22.5 Nm) (diag. 24 & 25).
Engine models V50, H50, H60, H70, VH50, VH60, VH70
require a flat and a belleville washer on bolts numbered
1, 3, and 7. Current production HM80 and HM100 use
flat washers only on bolts numbered 2 and 3 in conjunction
with the gas tank mounting bolts. All other head bolts on
HM80 and HM100 use a flat and a belleville washer on
each bolt.
Engine models V60, V70, TVM125, 140, 195, 220 require
a flat washer and a belleville washer on all head bolts.
2
5 3 7
ALL MODELS EXCEPT HM,VM, TVM170,195,220 24
BELLEVILLE WASHER
5 (CROWN TOWARD
9
BOLT HEAD)
7
3
2
1
6
8
4
TVM170,195,220,VM & HM MODEL ENGINES 25
1
FLAT
WASHER
INDICATES .010
OVERSIZE PISTON
PISTONS, RINGS, AND CONNECTING RODS
Piston
The piston should be checked for wear by measuring at
the bottom of the skirt 90 degrees from the piston pin
hole with a micrometer. Check the ring side clearance
using a feeler gauge with new ring. Clean all carbon from
the piston top and the ring grooves before measuring.
Visually inspect the piston skirt area for scoring or
scratches from dirt ingestion. If scoring or deep scratches
are evident, replace the piston.
If the cylinder bore needs re-sizing, an oversize piston
will be necessary. Oversize pistons are identified by the
imprinted decimal oversize value imprinted on the top of
the piston (diag. 26).
Rings
After the cylinder bore diameter has been checked and
is acceptable to rebuild, the ring end gap should be
checked using new rings. Place a new compression ring
squarely in the center of the ring travel area. Use the
piston upside down to push the ring down (diag. 28) and
measure the gap with a feeler gauge. The ring end gap
must be within the specification to have adequate oil
control (diag. 29). This procedure will assure correct piston
ring end gap measurement. Ring side clearance should
also be checked with a feeler gauge when using new
rings with an old piston (diag. 27).
Replace the rings in sets and install the piston, rings,
and rod assembly in the cylinder bore with the ring end
gaps staggered. When installing new rings in a used
cylinder, the cylinder wall should be de-glazed using a
commercially available de-glazing tool or hone.
PISTON MEASUREMENTS ARE TAKEN AT
BOTTOM OF SKIRT 90 0 FROM WRIST PIN HOLE
1ST COMPRESSION RING
CYLINDER
2ND
COMPRESSION
RING
26
SIDE CLEARANCE
3RD OIL
CONTROL RING
PISTON
27
PISTON RING
28
29
82
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