Yamaha MM700A Manual page 31

GENERAL INFORMATION
REMOVING BROKEN
SCREWS AND BOLTS
1. Center punch broken stud
3. Tap in screw extractor
CAUTION
Do not direct high-pressure water at steer-
ing bearings, carburetor hoses, wheel bear-
ings, suspension and electrical components,
or O-ring drive chains. The water forces the
grease out of the bearings and
the seals.
14. If special tools are required, have them available be-
fore starting the procedure. When special tools are re-
quired, they will be described at the beginning of the
procedure.
15. Make diagrams of similar-appearing parts. For in-
stance, crankcase bolts are often not the same lengths. Do
not rely on memory alone. Carefully laid out parts may
become disturbed, making it difficult to reassemble the
components correctly without a diagram.
16. Make sure all shims and washers are reinstalled in the
same location and position.
17. Whenever rotating parts contact a stationary part,
look for a shim or washer.
18. Use new gaskets if there is any doubt about the condi-
tion of old ones.
19. If self-locking fasteners are used, replace them with
new ones. Do not install standard fasteners in place of
self-locking ones.
2. Drill hole in stud
4. Remove broken stud
damage
may
20. Use grease to hold small parts in place if they tend to
fall out during assembly. Apply grease to electrical or
brake components.
Removing Frozen Fasteners
If a fastener cannot be removed, several methods may
be used to loosen it. First, apply penetrating oil such as
Liquid Wrench or WD-40. Apply it liberally and let it pen-
etrate for 10-15 minutes. Rap the fastener several times
with a small hammer. Do not hit it hard enough to cause
damage. Reapply the penetrating oil if necessary.
For frozen screws, apply penetrating oil as described,
then insert a screwdriver in the slot and rap the top of the
screwdriver with a hammer. This loosens the rust so the
screw can be removed in the normal way. If the screw
head is too damaged to use this method, grip the head with
locking pliers and twist the screw out.
Avoid applying heat unless specifically instructed, as it
may melt, warp or remove the temper from parts.
Removing Broken Fasteners
If the head breaks off a screw or bolt, several methods
are available for removing the remaining portion. If a
large portion of the remainder projects out, try gripping 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 screwdriver
(Figure 48).
If the head breaks off flush, use a screw extractor. To do
this, centerpunch the exact center of the remaining portion
of the screw or bolt. Drill a small hole in the screw and tap
the extractor into the hole. Back the screw out with a
wrench on the extractor (Figure 49).
Repairing Damaged Threads
Occasionally, threads are 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 (Figure 50).
To clean or repair spark plug threads, use a spark plug tap.
If an internal thread is damaged, it may be necessary to
install a Helicoil or some other type of thread insert. Fol-
low the manufacturer's instructions when installing the
insert.
If it is necessary to drill and tap a hole, refer to Table 10
for metric tap and drill sizes.
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