The new unloader pistons should be a loose
sliding fit in the unloader piston bores of the cylin-
If the crankshaft is fitted with oil seal rings, install
r i n g s . Position ball bearings and crankshaft in
crankcase making sure the drive end of the crank-
shaft is positioned as marked before disassembly.
DISCHARGE VALVES AND SEATS
Ii one end of the crankcase is counterbored for
If discharge valve seats merely show signs of
holding a bearing, be sure the crankshaft is installed
slight wear. they can be dressed by using a lapping
through the correct end of the crankcase.
stone, grinding compound and grinding tool. Install
C a r e f u l l y press crankshaft and bearings into
new discharge valves, valve springs, and cap nuts.
T h e discharge valve travel should be between
crankcase using arbor press.
.056"-.070" (1.42-1.77 mm) for the Tu-Flo 500.
Position a new rear end cover gasket over the
To test for leakage by the discharge valves apply
rear end of the crankcase making sure the oil hole
in the gasket lines up with the oil hole in the crank-
about 100 pounds (7 kg/cm) of air pressure through
case. Position end cover with oil seal ring, if used,
the cylinder head discharge port and apply soap
installed over crankcase and end cover gasket. The
suds at the discharge valves and seats. Leakage in
end cover should be positioned correctly in relation
the forming of soap bubbles is permissible.
to the oil holes in the gasket and crankcase. Secure
end cover to crankcase with cap screws and lock
If excessive leakage is found, leave the air pres-
sure applied, and with the use of a fibre or hard-
wood dowel and hammer, tap the discharge valves
If the opposite end cover requires an oil seal
off their seats several times. This will help the valves
which was removed on disassembly, a new seat
to seat and should reduce any leakage.
should be pressed into end cover. Position new end
cover gasket and carefully install end cover over
With the air pressure still applied at the discharge
crankshaft and to crankcase avoiding damage to
port of the cylinder head, check for leakage at the
the seal. Secure end cover with cap screw and lock
discharge valve cap nuts. No leakage is permissible.
INLET VALVES AND SEATS
If inlet valve seats show sign of slight nicks or
If new wrist pin bushings are to be used, they
scratches, they can be redressed with a fine piece
should be pressed into the connecting rods so that
of emery cloth or by lapping with a lapping stone,
the oil hole in the bushing lines up with the one in
grinding compound and grinding tool. If the seats
the rod. The new bushings should then be reamed
a r e excessively damaged to the extent that they
or honed to provide between 0.0001" (.002 mm) and
cannot be reclaimed. they should be replaced. The
0.0006" (.015 mm) clearance on the wrist pin. Posi-
dimension from the top of the cylinder block to the
tion connecting rod in piston and press in wrist pin
inlet valve seat should not exceed 0.145" (3.68 mm)
so that lockwire hole in the pin aligns with that of
nor be less than 0.101" (2.56 mm).
the piston. Install new lockwire through piston and
wrist pin and lock same by snapping short end into
Slightly worn or scratched inlet valves can be
lockwire hole at the bottom of the piston (Fig. 2).
reclaimed by lapping them on a piece of fine crocus
cloth on a flat surface, but it is suggested that new
inlet valves be installed.
pip-marks up (Fig. 11). Stagger the position of the
P r e l u b r i c a t e piston, piston rings, wrist pin and
INSTALLING CYLINDER BLOCK
connecting rod bearings with clean engine oil be-
Position cylinder block gasket and block on
crankcase according to markings made prior to dis-
Remove connecting bolts and bearing cap from
one connecting rod. Turn crankshaft so one of its
cure cylinder block to crankcase.