Yamaha MM700A Manual page 89

LUBRICATION, MAINTENANCE AND TUNE-UP
Clip
position
2.0
Use the information in Step I as a guideline
only. Because of variables that exist with
each individual machine, use the sparkplug
condition as the determining factor . W h e n in
doubt, always install a jet that results in
slightly richer mixture.
1. After determining the altitude and temperature range
in which the snowmobile will operate, determine the nec-
essary jet changes as follows:
Clip
position
2.5
Clip
Shim
2. Refer to Chapter Five for carburetor removal and in-
stallation, Then replace the main jets as required.
3. Reinstall the carburetor as described in Chapter Five.
4. Run the snowmobile at high speed and then stop the
engine.
5. Open the shroud and remove the spark plugs. Read the
spark plugs as described in this chapter.
6. Reinstall the spark plugs.
7. If necessary, change the main jets. Run the snowmo-
bile again, and read the spark plugs. Repeat the procedure
until satisfactory spark plug readings are obtained.
a. Refer to Table 17 and Table 18 and find the temper-
ature and altitude range in which the snowmobile
will be operated. Then cross reference the altitude
and temperature to obtain the new main jet size.
NOTE
Number one carburetor is at PTO (clutch)
end o f engine; number three carburetor is at
recoil starter end of engine.
For example, refer Table 18. When the ambient
to
temperature is -20' F (-29' C) at an altitude of 4000
the recommended main jet size for the
No. 1 carburetor is 141.3 and 140.0 for the No. 2
and 3 carburetors.
CA UTION
Do not run the engine without the air box in-
stalled as engine seizure may result.
WARNING
I f taking spark plug readings, the engine
will be HOT! Use caution as the fuel in the
float bowl spills out when the main jet cover
is removedfrom the bottom of the float bowl.
Have a fire extinguisher and an assistant
standing by when performing this proce-
dure.
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