
1-5
DESCRIPTION
DESCRIPTION
• The machine you have purchased may differ slightly from those shown in the following.
• Designs and specifications are subject to change without notice.
1. Clutch lever
2. Hot starter lever
3. Front brake lever
4. Throttle grip
5. Radiator cap
6. Fuel tank cap
7. Engine stop switch
8. Kickstarter crank
9. Fuel tank
10. Radiator
11. Coolant drain bolt
12. Rear brake pedal
13. Valve joint14. Fuel cock
15. Cold starter knob
16. Air filter
17. Drive chain
18. Shift pedal
19. Oil level check window
20. Front fork 

1-13
STARTING AND BREAK-IN
STARTING AND BREAK-IN
FUEL
Always use the recommended fuel as 
stated below. Also, be sure to use 
new gasoline the day of a race.
Use only unleaded gasoline. The 
use of leaded gasoline will cause 
severe damage to the engine inter-
nal parts such as valves, piston 
rings, and exhaust system, etc.
If knocking or pinging occurs, use a 
different brand of gasoline or higher 
octane grade.
• For refueling, be sure to stop the 
engine and use enough care not 
to spill any fuel. Also be sure to 
avoid refueling close to a fire.
• Refuel after the engine, exhaust 
pipe, etc. have cooled off.
HANDLING NOTE
Never start or run the engine in a 
closed area. The exhaust fumes 
are poisonous; they can cause 
loss of consciousness and death 
in a very short time. Always oper-
ate the machine in a well-ventilated 
area.
• The carburetor on this machine 
has a built-in accelerator pump. 
Therefore, when starting the en-
gine, do not operate the throttle 
or the spark plug will foul.
• Unlike a two-stroke engine, this 
engine cannot be kick started 
when the throttle is open be-
cause the kickstarter may kick 
back. Also, if the throttle is open 
the air/fuel mixture may be too 
lean for the engine to start.
• Before starting the machine, per-
form the checks in the pre-opera-
tion check list.
AIR FILTER MAINTENANCE
According to "CLEANING THE AIR 
FILTER ELEMENT" section in the 
CHAPTER 3, apply the foam-air-filter 
oil or its equivalent to the element. 
(Excess oil in the element may ad-
versely affect engine starting.)
STARTING A COLD ENGINE
1. Inspect the coolant level.
2. Turn the fuel cock to "ON".
3. Shift the transmission into neutral.
4. Fully open the cold starter knob 
"1".
5. Kick the kickstarter crank.
Do not open the throttle while kick-
ing the kickstarter crank. Other-
wise, the kickstarter crank may 
kick back.
6. Return the cold starter knob to its 
original position and run the en-
gine at 3,000–5,000 r/min for 1 or 
2 minutes.
Since this model is equipped with an 
accelerator pump, if the engine is 
raced (the throttle opened and 
closed), the air/fuel mixture will be too 
rich and the engine may stall. Also 
unlike a two-stroke engine, this model 
can idle.
Do not warm up the engine for ex-
tended periods of time.
STARTING A WARM ENGINE
Do not operate the cold starter knob 
and throttle. Pull the hot starter lever 
"1" and  start the engine by kicking 
the kickstarter crank forcefully with a 
firm stroke. As soon as the engine 
starts, release the hot starter lever to 
close the air passage.Restarting an engine after a fall
Pull the hot starter lever and start the 
engine. As soon as the engine starts, 
release the hot starter lever to close 
the air passage.
The engine fails to start
Pull the hot starter lever all the way 
out and while holding the lever, kick 
the kickstarter crank 10 to 20 times to 
clear the engine. Then, restart the en-
gine. Refer to "Restarting an engine 
after a fall".
Observe the following break-in 
procedures during initial operation 
to ensure optimum performance 
and avoid engine damage.
Recommended fuel:
Premium unleaded 
gasoline only with a re-
search octane number 
of 95 or higher.
Thrott
le 
grip 
oper-
ation*Cold 
start-
er 
knobHot 
start-
er le-
ver
Star
ting 
a 
cold 
en-
gineAir tem-
perature = 
less than 
5 °C (41 
°F)Open 
3 or 4 
timesON OFF
Air tem-
perature = 
more than 
5 °C (41 
°F)None ON OFF
Air tem-
perature 
(normal 
tempera-
ture) = be-
tween 5 
°C (41 °F) 
and 25 °C 
(77 °F)NoneON/
OFFOFF
Air tem-
perature = 
more than 
25 °C (77 
°F)None OFF OFF
Starting an en-
gine after a long 
period of timeNone ON OFF
Restarting a 
warm engineNone OFF ON
Restarting an 
engine after a 
fallNone OFF ON
* Operate the throttle grip before kick 
starting. 

3-3
MAINTENANCE INTERVALS
COOLING SYSTEM
Check coolant level and leakage●●
Check radiator cap operation●
Replace coolant●Every two years
Inspect hoses●
OUTSIDE NUTS AND BOLTS
Retighten●●Refer to "STARTING AND BREAK-
IN" section in the CHAPTER 1.
AIR FILTER
Clean and lubricate●●Use foam air-filter oil or equivalent oil.
Replace●
OIL FILTER
Replace●●
OIL STRAINER
Clean●
ENGINE GUARD
Replace●Breakage
FRAME
Clean and inspect●●
FUEL TANK, COCK
Clean and inspect●●
BRAKES
Adjust lever position and pedal 
height●●
Lubricate pivot point●●
Check brake disc surface●●
Check fluid level and leakage●●
Retighten brake disc bolts, cali-
per bolts, master cylinder bolts 
and union bolts●●
Replace pads●
Replace brake fluid●Every one year
FRONT FORKS
Inspect and adjust●●
Replace oil●●Suspension oil "S1"
Replace oil seal●
FRONT FORK OIL SEAL AND 
DUST SEAL
Clean and lube●●Lithium base grease
PROTECTOR GUIDE
Replace● ItemAfter 
break-
inEvery 
race 
(about 
2.5 
hours)
Every 
third 
(about 
7.5 
hours)Every 
fifth 
(about 
12.5 
hours)
As re-
quiredRemarks 

3-5
PRE-OPERATION INSPECTION AND MAINTENANCE
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage.P.3-6 – 7
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the fuel 
line for leakage.P.1-13
Engine oilCheck that the oil level is correct. Check the crankcase and oil line 
for leakage.P.3-9 – 10
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the 
clutch operates smoothly.P.3-7
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly 
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-7 – 8
Brakes Check the play of front brake and effect of front and rear brake. P.3-14 – 16
Drive chainCheck drive chain slack and alignment. Check that the drive chain 
is lubricated properly.P.3-17 – 18
WheelsCheck for excessive wear and tire pressure. Check for loose 
spokes and have no excessive play.P.3-20 –  21
SteeringCheck that the handlebar can be turned smoothly and have no ex-
cessive play.P.3-21 –  22
Front forks and rear shock 
absorberCheck that they operate smoothly and there is no oil leakage.
P.3-18 –  20
Cables (wires)Check that the clutch and throttle cables move smoothly. Check 
that they are not caught when the handlebars are turned or when 
the front forks travel up and down.—
Exhaust pipe Check that the exhaust pipe is tightly mounted and has no cracks. P.4-3 –  6
Rear wheel sprocket  Check that the rear wheel sprocket tightening bolt is not loose. P.3-17
Lubrication  Check for smooth operation. Lubricate if necessary. P.3-23
Bolts and nuts  Check the chassis and engine for loose bolts and nuts. P.1-15
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-7
SettingsIs the machine set suitably for the condition of the racing course 
and weather or by taking into account the results of test runs be-
fore racing? Are inspection and maintenance completely done?P.7-1 –  10 

3-6
ENGINE
ENGINE
CHECKING THE COOLANT LEVEL
Do not remove the radiator cap 
"1", drain bolt and hoses when the 
engine and radiator are hot. Scald-
ing hot fluid and steam may be 
blown out under pressure, which 
could cause serious injury. When 
the engine has cooled, place a 
thick towel over the radiator cap, 
slowly rotate the cap counter-
clockwise to the detent. This pro-
cedure allows any residual 
pressure to escape. When the 
hissing sound has stopped, press 
down on the cap while turning 
counterclockwise and remove it.
Hard water or salt water is harmful 
to the engine parts. You may use 
distilled water, if you can't get soft 
water.
1. Place the machine on a level 
place, and hold it in an upright po-
sition.
2. Remove:
• Radiator cap
3. Check:
• Coolant level "a"
Coolant level low→Add coolant.
1. Radiator
CHANGING THE COOLANT
Do not remove the radiator cap 
when the engine is hot.
Take care so that coolant does not 
splash on painted surfaces. If it 
splashes, wash it away with water.
1. Place a container under the en-
gine.
2. Remove:
• Coolant drain bolt "1"
3. Remove:
• Radiator cap
Drain the coolant completely.
4. Clean:
• Cooling system
Thoroughly flush the cooling sys-
tem with clean tap water.
5. Install:
• Copper washer 
• Coolant drain bolt
6. Fill:
• Radiator
•Engine
To specified level.
• Do not mix more than one type of 
ethylene glycol antifreeze con-
taining corrosion inhibitors for 
aluminum engine.
• Do not use water containing im-
purities or oil.
Handling notes of coolant:
The coolant is harmful so it should be 
handled with special care.
• When coolant splashes to your 
eye.
Thoroughly wash your eye with 
water and see your doctor.
• When coolant splashes to your 
clothes.
Quickly wash it away with water 
and then with soap.
• When coolant is swallowed.
Quickly make him vomit and take 
him to a doctor.
7. Install:
• Radiator cap
Start the engine and warm it up 
for a several minutes.
8. Check:
• Coolant level
Coolant level low→Add coolant.
CHECKING THE RADIATOR CAP
1. Inspect:
• Seal (radiator cap) "1"
• Valve and valve seat "2"
Crack/damage→Replace.
Exist fur deposits "3" →Clean or 
replace.
CHECKING THE RADIATOR CAP 
OPENING PRESSURE
1. Attach:
• Radiator cap tester "1" and adapt-
er "2"
Apply water on the radiator cap seal.
Coolant drain bolt:
10 Nm (1.0 m•kg, 7.2 
ft•lb)
Recommended coolant:
High quality ethylene 
glycol anti-freeze con-
taining anti-corrosion 
for aluminum engine
Coolant "1" and water 
(soft water) "2" mixing ra-
tio:
50%/50%
Coolant capacity:
1.00 L (0.88 Imp qt, 1.06 
US qt)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester 
adapter:
YU-33984/90890-01352 

3-9
ENGINE
6. Apply:
• Lithium soap base grease 
On the matching surface "a" on air 
filter element.
7. Install:
• Air filter element "1"
• Washer
• Fitting bolt
Align the projection "a" on filter guide 
with the hole "b" in air filter case.
CHECKING THE ENGINE OIL 
LEVEL
1. Start the engine, warm it up for 
several minutes, and then turn off 
the engine and wait for five min-
utes.
2. Place the machine on a level 
place and hold it up on upright po-
sition by placing the suitable 
stand under the engine.
3. Inspect:
• Oil level
The engine oil level should be be-
tween the minimum level mark "a" 
and maximum level mark "b".
Below the minimum level mark →
Add the recommended engine oil 
to the proper level.
• Engine oil also lubricates the 
clutch and the wrong oil types or 
additives could cause clutch 
slippage. Therefore, do not add 
any chemical additives or use en-
gine oils with a grade of CD or 
higher and do not use oils la-
beled "ENERGY CONSERVING 
II".
• Do not allow foreign materials to 
enter the crankcase.
4. Install:
• Oil tank cap
5. Start the engine and let it warm up 
for several minutes.
6. Turn off the engine and inspect 
the oil level once again.
Wait a few minutes until the oil settles 
before inspecting the oil level.
CHANGING THE ENGINE OIL
1. Start the engine and warm it up 
for several minutes, and then turn 
off the engine and wait for five 
minute.
2. Place the machine on a level 
place and hold it on upright posi-
tion by placing the suitable stand 
under the engine.
3. Place a suitable container under 
the engine.4. Remove:
• Lower engine guard "1"
• Bolt (oil tank) "2"
• Washer "3"
• Oil filler cap "4"
• Oil tank drain bolt "5"
• Crankcase oil drain bolt "6"
• Oil filter element drain bolt "7"
Drain the crankcase and oil tank 
of its oil.
5. Remove:
• Oil hose clamp "1"
• Bolt (oil hose)
• Oil hose "2"
• Oil strainer "3"
6. Inspect:
• Oil strainer
Clogged→Blow.
7. If the oil filter is to be replaced dur-
ing this oil change, remove the fol-
lowing parts and reinstall them. Fitting bolt:
2 Nm (0.2 m•kg, 1.4 
ft•lb)
Recommended brand: 
YAMALUBE
Recommended engine 
oil type
SAE10W-30, SAE 10W-
40, SAE 10W-50, SAE 
15W-40, SAE 20W-40 or 
SAE 20W-50
Recommended engine 
oilgrade
API service SG type or 
higher, JASO standard 
MA 

3-10
ENGINE
Replacement steps:
a. Remove the oil filter element cov-
er "1" and oil filter element "2".
b. Check the O-rings "3", if cracked 
or damaged, replace them with a 
new one.
c. Install the oil filter element and oil 
filter element cover.
8. Install:
• O-ring "1" 
• Oil strainer "2"
• Oil hose
• Bolt (oil hose)
• Oil hose clamp
9. Install:
• Copper washer 
• Oil filter element drain bolt
• Crankcase oil drain bolt• Oil tank drain bolt
• Lower engine guard
10. Fill:
• Engine oil
11. Check:
• Oil leakage
12. Install:
• Oil filler cap
• Washer (oil tank)
• Bolt (oil tank)
13. Check:
• Engine oil level
CHECKING THE OIL PRESSURE
1. Check:
• Oil pressure
Checking steps:
a. Slightly loosen the oil pressure 
check bolt "1".
b. Start the engine and keep it idling 
until oil starts to seep from the oil 
pressure check bolt. If no oil 
comes out after one minute, turn 
the engine off so it will not seize.
c. Check oil passages and oil pump 
for damage or leakage.
d. Start the engine after solving the 
problem(s) and recheck the oil 
pressure.e. Tighten the oil pressure check 
bolt.
ADJUSTING THE PILOT SCREW
1. Adjust:
• Pilot screw "1"
Adjustment steps:
To optimize the fuel flow at a smaller 
throttle opening, each machine's pilot 
screw has been individually set at the 
factory. Before adjusting the pilot 
screw, turn it in fully and count the 
number of turns. Record this number 
as the factory-set number of turns 
out.
a. Turn in the pilot screw until it is 
lightly seated.
b. Turn out the pilot screw by the 
factory-set number of turns.
ADJUSTING THE ENGINE IDLING 
SPEED
1. Start the engine and thoroughly 
warm it up.
2. Adjust:
• Engine idling speed
Adjustment steps:
a. Adjust the pilot screw. 
Refer to "ADJUSTING THE PI-
LOT SCREW" section. Oil filter element cover:
10 Nm (1.0 m•kg, 7.2 
ft•lb)
Oil strainer:
9 Nm (0.9 m•kg, 6.5 
ft•lb)
Bolt (oil hose):
8 Nm (0.8 m•kg, 5.8 
ft•lb)
Oil hose clamp:
2 Nm (0.2 m•kg, 1.4 
ft•lb)
Oil filter element drain 
bolt:
10 Nm (1.0 m•kg, 7.2 
ft•lb)
Crankcase oil drain bolt:
20 Nm (2.0 m•kg, 14 
ft•lb)
Oil tank drain bolt:
18 Nm (1.8 m•kg, 13 
ft•lb)
Lower engine guard:
10 Nm (1.0 m•kg, 7.2 
ft•lb)
Oil quantity:
Periodic oil change:
0.95 L (0.84 Imp qt, 
1.00 US qt)
With oil filter replace-
ment:
1.05 L (0.92 Imp qt, 
1.11 US qt)
Total amount:
1.20 L (1.06 Imp qt, 
1.27 US qt)
Bolt (oil tank):
4 Nm (0.4 m•kg, 2.9 
ft•lb)
Oil pressure check bolt:
10 Nm (1.0 m•kg, 7.2 
ft•lb)
Pilot screw (example):
2 turns out
*2-1/4 turns out
* For EUROPE 

4-37
OIL FILTER ELEMENT AND WATER PUMP
REMOVING THE IMPELLER 
SHAFT
1. Remove:
• Impeller "1"
• Washer "2"
• Impeller shaft "3"
Hold the impeller shaft on its width 
across the flats "a" with spanners, 
etc. and remove the impeller.
REMOVING THE OIL SEAL
It is not necessary to disassemble the 
water pump, unless there is an abnor-
mality such as excessive change in 
coolant level, discoloration of coolant, 
or milky transmission oil.
1. Remove:
• Bearing "1"
2. Remove:
• Oil seal "1"CHECKING THE OIL DELIVERY 
PIPE
1. Inspect:
• Oil delivery pipe "1"
Bend/damage→Replace.
Clogged→Blow.
CHECKING THE IMPELLER SHAFT
1. Inspect:
• Impeller shaft "1"
Bend/wear/damage→Replace.
Fur deposits→Clean.
CHECKING THE IMPELLER SHAFT 
GEAR
1. Inspect:
• Gear teeth "a"
Wear/damage→Replace.
CHECKING THE BEARING
1. Inspect:
•Bearing
Rotate inner race with a finger.
Rough spot/seizure→Replace.CHECKING THE OIL SEAL
1. Inspect:
• Oil seal "1"
Wear/damage→Replace.
INSTALLING THE OIL SEAL
1. Install:
• Oil seal "1" 
• Apply the lithium soap base grease 
on the oil seal lip.
• Install the oil seal with its manufac-
ture's marks or numbers facing the 
right crankcase cover "2".
2. Install:
• Bearing "1"
Install the bearing by pressing its out-
er race parallel.