7. Valves, Seats and Guides
b. With a micrometer, check journal for out of
round. Correct crankpin size is 1.186. If out of
a. Check clearance of old valve stems in guides.
round, replace shaft or regrind to .010
b. If worn, replace valve guides. To remove,
undersize.
guides, we recommend that they be driven
c. Check gear, keyway and tapered part of shaft
down into the valve chamber and carefully
for wear. If worn, replace shaft.
broken, taking care to not damage cylinder
block. It will be necessary to ream guides to
4. Connecting Rod
gain correct fit.
a. Check rod for wear, score marks, running
clearances, and side clearance. Replace rod if
c. Consult Parts Identification Section for correct
worn beyond high limit of clearances shown in
valve number.
Some applications require
table on page 23.
special valves.
b. Connecting rod bearings are an integral part of
d. Intake valve seat is normally machined into
the rod and not separately replaceable.
block. Separate inserts are sometimes used.
c. Connecting rods .010 undersize are available
e. The exhaust valve seat is a moly-nickel chrome
for reground crankshafts.
or Stellite insert.
5. Piston
f. The seating surfaces should be held as nearly
as possible to 1/32" in width. Seats with more
a. If cylinder block does not require reboring and
than 1/16" seating surface should be
old piston is free of score and scuff marks,
reconditioned with 45 and 15 cutters and
check piston ring grooves and lands.
ground to form proper seat.
b. Clean grooves and fit NEW rings.
c. With rings in place, check clearance with a
ASSEMBLY OF ENGINE
feeler gauge. Replace piston if a .005 feeler
can be inserted between ring and land.
1. Install rear main bearing by pressing it into cylinder
block with shielded side facing to inside of block. Figure
d. When inserted in cylinder, piston ring end
clearance should be between .007 and .017.
e. Never re-use old rings.
2. Governor Shots
6. Piston Pins
a. Current production engines have a cross shaft
with an extension riveted in place to line up with
a. Very little wear takes place on piston pin or in
governor gear. Figure 16. A needle bearing is
piston bosses.
provided (in block) to hold cross shaft in
b. Assemble piston to connecting rod. Use a
alignment.
commercial rod aligner. Piston must be square
b. Engines manufactured before serial No.
with cylinder bore and crankshaft.
202305 have a short-angle arm and use bushing
nut for a bearing and for shaft alignment.
3. To Install Governor
a. Place cylinder block on its side. Slide governor
shaft into place from inside of block.
b. Place speed control disc on governor bushing
nut and thread bushing nut into block, clamping
throttle bracket into place.
c. The governor shaft can be adjusted for end
clearance by moving needle bearing in block.
Set bearing to allow a slight back-and-forth
movement of the shaft.
d. Before serial 202305, a lock ring is used to hold
governor shaft in place.
Figure 15
Installing Rear Main Bearing
73
