Yamaha MM700A, Manual, Page: 87 / 282

LUBRICATION, MAINTENANCE AND TUNE-UP 81
High speed tuning
Mid-range
speed tuning
Low speed tuning
other than those specified, adjust the carburetors accord-
ingly.
Figure 47 illustrates the different carburetor circuits
and how they overlap during engine operation. Refer to
the tables at the end of Chapter Five for carburetor specifi-
cations at sea level conditions.
Before tuning the carburetor, adjust the carburetor (in-
cluding synchronization) and oil pump adjustment as de-
scribed in this chapter:
NOTE
Changes in port shape and smoothness, ex-
pansion chamber, carburetor, etc., also re-
quire jetting changes because these factors
alter the engine's ability
to breathe. When
installing equipment or when
the engine has been equipment
manufacturers often include a tech sheet
listing suitable jetting changes to corre-
spond to their
or
Take this information into account along
with altitude and temperature conditions
previously mentioned.
NOTE
It is important to note that the following jet-
ting guidelines are guidelines only. Individ-
ual adjustments vary because of altitude,
temperature and snow conditions. Use
spark plug condition as a guideline when
and adjusting the carburetor.
Low-speed tuning
Low-speed operation, less than 1/8 throttle opening, is
controlled by the pilot air system. Refer to the Idle Speed
Idle Mixture section to adjust the carbure-
tor for low-speed operation.
If adjusting the pilot air screw does not provide opti-
mum performance, it may be necessary to change the pilot
jet. Refer to Chapter Five
for replacement of the pilot jet.
Pilot jets are identified by a number (Figure 48). As the
pilot numbers increase, the fuel mixture
Changes in altitude and temperature may require
changing the sizes of pilot jets in the carburetors, as
well as the main jets and jet needle clip position. Refer to
recommended pilot jet sizes in
Table 17 and Table 18.