Yamaha JT1 Series Assembly Manual page 14

8 Obtain a dial indicator
and adapter Insert the
dial indicator into the
adapter Secure It by
tightening the setscrew
at the side of the adapt-
er finger tight.
9 Screw the adapter int o
the spark plug hole .
10 Turn the magneto rotor
to the point w here the
dial indicator hesitat es
Just before reversing d1 -
rectIon This ,s Top
Dead Center - w here
the piston ,s at ,ts high-
est point in the cylinder.
M ove the rotor back and
forth several times to
make sure you are ex-
actly at this point.
1 1 When the piston Is at
Top Dead Center. line up
the 0 on the face of the
dial indicat or w ith the
needle by rotating the
dial face Turn the po int
checker toggle sw itch to
ON
12 Turn the rotor clockw ise
(backw ard) until t he dial
indicator needle makes
2 full revolutions of the
dial Then. w hile w atch-
ing the point checker.
rotate the rotor counter-
clockw ise (forward) un -
til the point checker
needle moves A t this
point . the d ial indicator
20
_)
DIAL INDICATOR
needle should be at 20.
(Tolerance is 3 marks
on either side of 20.)
Note
One complete revolutio n
of the needle equals 1
m m of p iston travel.
Therefore. when the
needle moves back 2
revolutions. then for-
ward to 20. it means
the p iston is at a final
position of
1
.8 mm be-
low Top Dead Center.
Overshooting , and re-
turning to 20 is done to
t ake up any slack in
gears and bearings.
13. If the point c hecke r nee-
dle moved as the piston
was brought to th e 1.8
mm point. t iming and
point gap is correct . Go
to step 16. If it doesn't .
t he points must be ad-
justed to open at
1.8
mm. Continue with
step 14.
14.
Make sure piston is at
1.8
mm (20 on the dial
indicator).
15.
Adjust the points by
loosening the point se-
curing screw and mov-
ing the plate with a
screwdriver. When the
point checker needle
moves. it means the
points are just beginning
to open. At this point.
adjustment is correct.
Tighten the securing
screw.
16. Repeat step 12 and 13
to check your work. Re-
adjust the points if nec-
essary.
17. Turn the point checker
to OFF and disconnect
the leads. Remove the
d ial indicator and adapt-
e r fro m th e spark plug
hole.
18. Using a wi re type feeler
gage, c heck that the
spark plug gap is 0 .020
to 0 .024 inch (0 .5 to
0 .6 mm). Adj ust it if
nec essary.
19. Insta ll the spark pl ug
and t o rque it t o 20 t o
25 lb-ft. Snap t he w ire
lead c ap assembly on
the spark plug.
20. Install the generator
cove r.
21