Yanmar 1GM User Manual page 24

GENE RAL INFORMATION
If a large portion of the remainder projects out, try grip -
ping it with locking pliers. If the projecting portion is too
small, file
it
to fit a wrench or cut a slot in
it
to
fit
a screw-
drive r. See Figure 44.
Ifthe head breaks off flush, use a screw extractor. To do
this, centerpunch the remaining portion of the screw or
bo lt. Drill a small hole in the screw and lap the extractor
into the hole . Back the screw out with a wrench on the ex-
tractor. See Figu re 45 .
Remedying St r ipped T hre ads
Occasionally, threads arc stripped through carelessness
or impact damage. Often the threads can be repaired by
running a tap (for internal threads on nuts) or die (for ex-
ternal threads on bolts) through the threads. Sec Figure
46 . To clean or repair spark plug threads, a spark plug tap
can be used.
NOTE
Tap and dies can be purchased individually
or in a set as shown in Figu re 47.
If an internal thread is damaged, it may be necessary to
instal l a Helicoil ( Figu re
48) or some other type of thread
17
' -__ Filed
Slo tted
insert . Follow the manufacturer's instructions when in-
stalling their insert.
Ifi t is necessary to drill and tap a hole, refer to Ta ble 4
for metric tap and drill sizes.
Removing Broken or Damag ed St uds
If a stud is broken or the threads severely damaged, per-
form the following. A tube ofLoctite 27 1 (red), two nuts ,
two wrenches and a new stud will be required during this
procedure.
I . Thread IwO nuts onto the damaged stud. Then tighten
the two nuts against each other so that they are locked .
NOTE
Ifthe threads on the damaged stud do flat al-
low installation of the two nuts, remove the
stud with a stud remover or a pair oflocking
pliers.
2. Tum the bottom nut counterclockwise and unscrew the
stud.
3. Clean the threads with solvent or electrical contact
cleaner and allow them 10dry thoroughly.
4. Install two nuts on the top half of the new stud as in
Step 1. Make sure they arc locked securely.
5. Coat the bottom half of a new stud with Loctite 271
(red).
6. Tum the top nut clockwise and thread the new stud se-
curely.
7. Remove the nuts and repeat for each stud as required.
8. Follow Loctitc's directions on cure time before assem-
bling the component.
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