Starting And Break-In; Starting A Cold Engine; Starting A Warm Engine; Break-In Procedures - Yamaha YTZ250S 1986 Service Manual

STARTING AND BREAK-IN
Before starting the machine, perform the
checks in the preoperation check list.
WARNING:
• Avoid "wheelies" and jumping to pre-
vent loss of control.
• Always put your feet on the footrests
during operation. If you should take
your feet off the footrests, they may
contact the rear wheels.
• Never start or run the engine in a clos-
ed area. The exhaust fumes are pois-
onous; they can cause loss of con-
sciousness and death in a very short
time. Always operate the machine in
a well-ventilated area.
Starting a Cold Engine
Shift the transmission into neutral. Turn on
the fuel cock and full open the starter knob on
the carburetor. With the throttle completely
closed, kickstart the engine with a smooth, firm
stroke. Half-open the starter knob, run the
engine at idle or slightly higher until it warms
up; this usually takes about one or two
minutes. The engine is warmed up when it
responds normally to the throttle with the
starter knob pushed completely down.
Do not warm up the engine for extended
periods.
Starting a Warm Engine
Do not raise the starter knob. Open the throt-
tle slightly and kickstart the engine with a
smooth, firm stroke.
Observe the following break-in pro-
cedures during initial operation to ensure
optimum performance and avoid engine
damage.
1-16
Break-in Procedures
1. Before starting the engine, fill the fuel
tank with a break-in oil-fuel mixture of
12: 1 to 14:
1.
2. Perform the preoperation checks on the
machine.
3. Start and warm up the engine. Check the
idle speed, and check the operation of
the controls and the engine stop switch.
4. Operate the machine in the lower gears
at moderate throttle openings for five to
eight minutes. Stop and check the spark
plug condition; it will show a rich condi-
tion during break-in.
5. Allow the engine to cool. Restart the
engine and oeprate the machine as in the
step above for five minutes. Then, very
briefly shift to the higher gears and check
full-throttle response. Stop and check
the spark plug.
6. After again allowing the engine to cool,
restart and run the machine for five more
minutes.
Full throttle and the higher gears may be
used, but sustained full-throttle opera-
tion should be avoided. Check the spark
plug condition .
7. Allow the engine to cool, remove the top
end, and inspect the piston and cylinder;
instructions for this are described
Chapter 3 "CYLINDER HEAD". Remove
any high spots on the piston with
6OO-grit, wet sandpaper. Clean all com-
ponents and carefully reassemble the top
end.
8.
Drain the break-in oil-fuel mixture from
the fuel tank and refill with the specified
mix. Check the entire machine for loose
screws, bolts, and nuts.
9. Restart the engine and check the opera-
tion of the machine throughout its entire
operating range. Stop and check the
spark plug , condition. Restart the
machine and operate it for about 10 to 15
more minutes. The machine will now be
ready to race.