Rotax 912-UL - 9.4 Electric system

Startingwith engine
no.3,792.653,
only
inlet
side
is furnished with
valve stem seal.
Valve
stem
seal on the exhaust
valve
is
to be
removed.
Exchange indurated valve
stem
seals.
If
the engine
'has
been run
hot',
check
in
any
case
hardness
of cylinder
head material.
Minimum hardness 65 HB.
If
need be,
the tapped
hole for spark
plug
can be repaired
by
utilizing a
"heli-coil"
thread insert. Basically
this
repair
includes
reboring of the
dam-
aged thread,
tapping with a special tap
and
fitting
of
the
"heli-coil"
insert,
into
the newly
tapped
hole. After fit-
ting
the
"heli-coil"
break off bent end O by
turning back, and
remove it.
6.6.3) Valve
guide:
Check
inside
diameter and
gliding
face
of
valve
guide.
Dimension
valve
guide
intemal
dia.
valvc
guide
cxtcmal
dia.
inrcrferencc
fit in
cylindcr
hcad
valvc
stem dia.
cleanncc
of
valve stcm
new mm
(in)
wear limit mm
(in.)
7,006+ 7,018
(
0,276) 7,15
(0281)
12,O64+ 12,U5
(
0,474) 12,M4(0,475)
0,O16+
0,075
(0,002 +
0,003) 0,046(0,002)
6,965+ 6,980
(
0,n4) 6,94
(0,273)
0,A26+ 0,053
(0,001+
0,0O2) 0,15
(0,006)
If wear
has
reached the specified
limits, renew valve
guide.
Remove
valve spring
retainer. Knock
off the
part
of
camshaft chamber O.
The
guide
will
break at
groove
O
and can be
pressed
out
in
direction
of
combustion cham-
ber,
using
a suitable,
stepped
punch.
Prior to
pressing
in
a
new valve
guide
coat
lower
part
@
of the
guide
with slide
paste
Molykote
G-N.
The fitted valve
guide
is
to be
reamed
to diameter
7,006
+7,018
mm
(
0,276in.). Subsequently
inspectvalve seat,
rework as required and
check
valve for tightness.
Exchange ofvalve
guide
on
cold en-
gine.
the
guide
projecting
into
I
NOTE: