Yamaha JT1 Series Service Manual page 79

JTl
MOTORCYCLE
SERVICE NEWS
YAMAHA INTERNATIONAL CORPORATION
MONTEBELLO, CALIFORNIA
DATE
12/2/70
ROTARY VALVE INSTALLATION (TIMING)
NUMBER
256
PAGE
I
The JTl rotary valve mounts to the crankshaft in a slightly different
manner than previous Yamaha rotary valve models. This requires
special valve installation instructions which are given below.
A collar fits over the crankshaft (notch in collar fits over pin
in shaft), then the valve fits over the collar.
To install the
valve in proper relation to the crankshaft, the two indentations
in the outer valve surface must line up with the pin in the
crankshaft.
Rotary valve timing can also be checked by rotating the piston to
top dead center (indicated with dial indicator) and checking that
the valve closing edge just lines up with the left edge of the
intake port (see drawing).
PIN LOCATION NOTE: The locating pin in the shaft is removable.
Although the pin hole is drilled thru the shaft, permitting the
pin to protrude from either end of the hole, follow factory
installation recommendations. Position the pin to protrude out
of the hole end 100° from the crank pin. However, no matter
which end the pin extends from, the rotary valve can be correctly
timed by lining up the valve closing edge with the intake port •
. -
,,-
..
·, PISTON AT TDC
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