Yamaha MM700A, Manual, Page: 107 / 282

ENGINE 101
Inspection
1. Wipe away any soft deposits from the cylinder head
(Figure
17). Carefully remove hard deposits with a wire
brush or a soft metal scraper. Be careful not to gouge the
aluminum surfaces. Burrs created from improper cleaning
might cause preignition.
NOTE
Always use an aluminum thread fluid or ker-
osene on the thread chaser and cylinder
threads when performing Step 2.
2. After removing the spark plug. check the spark plug
threads in the cylinder head for any carbon buildup or
cracking. The carbon can be removed with a
14 spark
plug thread chaser. After cleaning the threads, reinstall the
spark plug and make sure it can be threaded into the cylin-
der head completely.
3. Use a straightedge and feeler gauge to measure the
flatness of the cylinder head. Small imperfections or
slight can be removed by resurfacing the cylin-
der head as follows:
a. a piece of 400-600 grit wet emery sandpaper to
a piece of thick plate glass or surface plate (Figure
18).
Slowly resurface the head by moving it in
lire-eight patterns on the sandpaper.
Rotate the head several times to avoid removing too
much material from one side. Check progress often
with the straightedge and feeler gauge.
d. If the cylinder head
warp
still exceeds the service
limit, it will be necessary to have the head resur-
faced by a machine shop familiar with snowmobile
and motorcycle service. Note that removing