Yamaha MM600D, Manual

Page: 85 / 282

LUBRICATION, MAINTENANCE AND TUNE-UP 79
greatly simplifies ignition timing and makes the ignition
system much less susceptible to failures caused by dirt,
moisture and wear.
The ignition timing is controlled by the CDI box and is
not adjustable. Incorrect ignition timing may be due to a
faulty
box, damaged flywheel key or damaged
keyway in the crankshaft or flywheel. Refer to Chapter
Six.
Carburetor Adjustment
Throttle synchronization
For maximum engine performance, all cylinders must
work equally. If one cylinder's throttle valve opens ear-
lier, that cylinder will be required to work harder. This
causes poor acceleration, rough
performance and
engine overheating. For proper carburetor synchroniza-
tion, all throttle valves must lift at the same time.
Check carburetor synchronization at each tune-up or
whenever the engine suffers from reduced performance.
Perform the following procedure to check and adjust car-
buretor synchronization.
1.
Remove the carburetors (Figure 40) as described in
Chapter Five.
2. Rotate the idle speed screw (A, Figure 40) so the throt-
tle valve height (Figure 41) on the center carburetor
Figure 40) is 1.2 mm (0.047 in.).
3. Check the throttle
height on both outer carbure-
tors (C, Figure 40). If the throttle valve height on the outer
carburetors is not 1.2
(0.047 in.), proceed as follows:
a. Remove the top cover (Figure 42) on the outer car-
buretors requiring adjustment.
b. Loosen the jam nut (A, Figure 43) and rotate the ad-
juster to adjust the throttle valve height.
Retighten the jam nut.
Operate the throttle two or three times, then recheck
the valve height on all three carburetors.
d. Reinstall the top covers.
4. Reinstall the carburetors as described in Chapter Five.
5. Adjust engine idle speed as described in this section.
Throttle lever free play
Refer to the previous section in this chapter and adjust
throttle lever free play. After performing throttle free play
adjustment, check the oil pump cable adjustment as
scribed in this chapter.
Starter cable adjustment
Incorrect starter cable (choke) adjustment can cause er-
ratic engine operation (not enough cable slack) or hard
starting (too much cable slack).
1.
Open the shroud.
2. Check the starter cable from the control lever to the
carburetors for damage. If the cables are good, perform
the following.
3.
Position the control lever on the dash to its OFF posi-
tion.
4. Measure the carburctor lever free play as shown in
Figure 44. Lever free play should be 0.5-1.5 mm
(0.02-0.06 in.).
5. If free play is incorrect, loosen the jam nut on the cable
adjuster (Figure 44) and rotate the adjuster. Hold the ad-
juster and tighten the jam nut. Recheck free play.
Idle speed and idle mixture adjustment
The pilot mixture screw, as well as the pilot jet inside
the carburetor, controls the idle fuel mixture. The pilot
mixture screw (Figure 45) controls mixture adjustment
when the throttle is opened from idle to the full open posi-
tion quickly and when the engine is
run at half-throttle.
Turning the pilot mixture screw clockwise leans the fuel