check engine YAMAHA YZ250F 2011 User Guide
Page 56 of 196
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 
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3-7
ENGINE
3. Radiator cap
2. Apply the specified pressure.
3. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds→
Replace.
CHECKING THE COOLING 
SYSTEM
1. Inspect:
• Coolant level
2. Attach:
• Radiator cap tester "1" and adapt-
er "2"
3. Apply the specified pressure.
• Do not apply pressure more than 
specified pressure.
• Radiator should be filled fully.
4. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds→
Repair.
•Radiator "1"
• Radiator hose joint "2"
Coolant leakage→Repair or re-
place.
• Radiator hose "3"
Swelling→Replace.ADJUSTING THE CLUTCH LEVER 
POSITION
1. Adjust:
• Clutch lever position
Clutch lever position adjustment 
steps:
a. Loosen the locknuts "1".
b. Turn the adjusting bolt "2" until the 
clutch lever position "a" is in the 
desiered position  .
c. Tighten the locknuts.
2. Adjust:
• Clutch cable free play
Refer to "ADJUSTING THE 
CLUTCH CABLE FREE PLAY".
ADJUSTING THE CLUTCH CABLE 
FREE PLAY
1. Check:
• Clutch lever free play "a"
Out of specification→Adjust.
2. Adjust:
• Clutch lever free play
Clutch lever free play adjustment 
steps:
a. Loosen the locknuts "1".
b. Turn the adjuster "2" until free 
play "a" is within the specified lim-
its.
c. Tighten the locknuts.
• Before adjustment, expose the ad-
juster by moving the boot "3" and 
cap "4" away.
• Make minute adjustment on the le-
ver side using the adjuster "5".
• After adjustment, check proper op-
eration of clutch lever.
3. Install:
•Cap "1"
• Boot "2"
Place the tip "a" of the cap in the boot.
ADJUSTING THE THROTTLE 
CABLE FREE PLAY
1. Check:
• Throttle grip free play "a"
Out of specification→Adjust. Radiator cap opening 
pressure:
110 kPa (1.1 kg/cm
2, 
15.6 psi)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester 
adapter:
YU-33984/90890-01352
Standard pressure:
180 kPa (1.8 kg/cm
2, 
25.6 psi)
Locknut:
5 Nm (0.5 m•kg, 3.6 
ft•lb)
Clutch lever free play "a" 
:
7–12 mm (0.28–0.47 in)
Locknut:
4 Nm (0.4 m•kg, 2.9 
ft•lb)
Throttle grip free play 
"a":
3–5 mm (0.12–0.20 in) 
Page 58 of 196
3-8
ENGINE
2. Adjust:
• Throttle grip free play
Throttle grip free play adjustment 
steps:
a. Slide the adjuster cover.
b. Loosen the locknut "1".
c. Turn the adjuster "2" until the 
specified free play is obtained.
d. Tighten the locknut.
Before adjusting the throttle cable 
free play, the engine idle speed 
should be adjusted.
After adjusting the throttle cable 
free play, start the engine and turn 
the handlebar to right and left and 
make sure that the engine idling 
does not run faster.
LUBRICATING THE THROTTLE
1. Remove:
• Cover (throttle cable cap) "1"
• Cover (grip cap) "2"
• Throttle grip cap "3"
2. Apply:
• Lithium soap base grease
On the throttle cable end "a".3. Install:
• Throttle grip cap
• Screw (throttle grip cap)
• Cover (grip cap)
• Cover (throttle cable cap)
ADJUSTING THE HOT STARTER 
LEVER FREE PLAY
1. Check:
• Hot starter lever free play "a"
Out of specification→Adjust.
2. Adjust:
• Hot starter lever free play
Hot starter lever free play adjust-
ment steps:
a. Loosen the locknut "1".
b. Turn the adjuster "2" until free 
play "a" is within the specified lim-
its.
c. Tighten the locknut.
After adjustment, check proper oper-
ation of hot starter.
CLEANING THE AIR FILTER 
ELEMENT
Proper air filter maintenance is the 
biggest key to preventing premature 
engine wear and damage.
Never run the engine without the 
air filter element in place; this 
would allow dirt and dust to enter 
the engine and cause rapid wear 
and possible engine damage.
1. Remove:
• Seat
• Fitting bolt "1"
• Washer "2"
• Air filter element "3"
• Air filter guide "4"
2. Clean:
• Air filter element
Clean them with solvent.
After cleaning, remove the remaining 
solvent by squeezing the element.
• Do not twist the element when 
squeezing the element.
• Leaving too much of solvent in 
the element may result in poor 
starting.
3. Inspect:
• Air filter element
Damage→Replace.
4. Apply:
• Foam-air-filter oil or equivalent oil 
to the element
Squeeze out the excess oil. Element 
should be wet but not dripping.
5. Install:
• Air filter guide "1"
Align the projection "a" on filter guide 
with the hole "b" in air filter element.
Locknut:
4 Nm (0.4 m•kg, 2.9 
ft•lb)
Screw (throttle grip cap):
4 Nm (0.4 m•kg, 2.9 
ft•lb)
Hot starter lever free play 
"a":
3–6 mm (0.12–0.24 in)
Locknut:
4 Nm (0.4 m•kg, 2.9 
ft•lb) 
Page 59 of 196
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 
Page 60 of 196
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):
1-3/4 turns out 
Page 61 of 196
3-11
ENGINE
b. Turn the throttle stop screw "1" 
until the specified engine idling 
speed.
Using a digital engine tachometer for 
idle speed adjustment, detect the en-
gine idling speed by bringing the 
sensing element "c" of the engine ta-
chometer close to the ignition coil "2".
ADJUSTING THE VALVE 
CLEARANCE
• This section is intended for those 
who have basic knowledge and skill 
concerning the servicing of Yama-
ha motorcycles (e.g., Yamaha deal-
ers, service engineers, etc.) Those 
who have little knowledge and skill 
concerning servicing are requested 
not to undertake inspection, adjust-
ment, disassembly, or reassembly 
only by reference to this manual. It 
may lead to servicing trouble and 
mechanical damage.
• The valve clearance should be ad-
justed when the engine is cool to 
the touch.
• The piston must be at Top Dead 
Center (T.D.C.) on compression 
stroke to check or adjust the valve 
clearance.
1. Remove:
•Seat
•Fuel tank
Refer to "SEAT, FUEL TANK 
AND SIDE COVERS" section in 
the CHAPTER 4.
2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFTS" section 
in the CHAPTER 4.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw 
"2"
• O-ring
4. Check:
• Valve clearance
Out of specification→Adjust.
Checking steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
b. Align the T.D.C. mark "a" on the 
rotor with the align mark "b" on the 
crankcase cover when piston is at 
T.D.C. on compression stroke.
In order to be sure that the piston is at 
Top Dead Center, the punch mark "c" 
on the exhaust camshaft and the 
punch mark "d" on the intake cam-
shaft must align with the cylinder 
head surface, as shown in the illustra-
tion.
c. Measure the valve clearance "e" 
using a feeler gauge "1".
Record the measured reading if the 
clearance is incorrect.
5. Adjust:
• Valve clearance
Adjustment steps:
a. Remove the camshaft (intake and 
exhaust).
Refer to "CAMSHAFTS" section 
in the CHAPTER 4.
b. Remove the valve lifters "1" and 
the pads "2".
• Place a rag in the timing chain 
space to prevent pads from falling 
into the crankcase.
• Identity each valve lifter and pad 
position very carefully so that they 
can be reinstalled in their original 
place.
To increase idle speed→Turn the 
throttle stop screw "1" in "a".
To decrease idle speed→Turn the 
throttle stop screw "1" out "b".
Engine idling speed:
1,900–2,100 r/min
Valve clearance (cold):
Intake valve:
0.12–0.17 mm 
(0.0047–0.0067 in)
Exhaust valve:
0.17–0.22 mm 
(0.0067–0.0087 in) 
Page 67 of 196
3-17
CHASSIS
CHECKING THE SPROCKET
1. Inspect:
• Sprocket teeth "a"
Excessive wear→Replace.
Replace the drive sprocket, rear 
wheel sprocket and drive chain as a 
set.
CHECKING THE DRIVE CHAIN
1. Measure:
• Drive chain length (15 links) "a"
Out of specification→Replace.
• While measuring the drive chain 
length, push down on the drive 
chain to increase its tension.
• Measure the length between drive 
chain roller "1" and "16" as shown.
• Perform this measurement at two or 
three different places.
2. Remove:
• Master link clip
•Joint "1"
• Drive chain "2"3. Clean:
• Drive chain
Place it in kerosene, and brush off 
as much dirt as possible. Then re-
move the drive chain from the ker-
osene and dry the drive chain.
4. Check:
• Drive chain stiffness "a"
Clean and oil the drive chain and 
hold as illustrated.
Stiff→Replace the drive chain.
5. Install:
• Drive chain "1" 
•Joint "2"
• Master link clip "3" 
Be sure to install the master link 
clip to the direction as shown.
a. Turning direction
6. Lubricate:
• Drive chainADJUSTING THE DRIVE CHAIN 
SLACK
1. Elevate the rear wheel by placing 
the suitable stand under the en-
gine.
2. Check:
• Drive chain slack "a"
Above the seal guard installation 
bolt.
Out of specification→Adjust.
Before checking and/or adjusting, ro-
tate the rear wheel through several 
revolutions and check the slack sev-
eral times to find the tightest point. 
Check and/or adjust the drive chain 
slack with the rear wheel in this "tight 
chain" position.
3. Adjust:
• Drive chain slack
Drive chain slack adjustment 
steps:
a. Loosen the axle nut "1" and lock-
nuts "2".
b. Adjust the drive chain slack by 
turning the adjusters "3".
c. Turn each adjuster exactly the 
same amount to maintain correct 
axle alignment. (There are marks 
"a" on each side of the drive chain 
puller alignment.) NOTICE: Im-
proper drive chain slack will 
overload the engine aswell as 
other vital parts of the motorcy-
cle and can lead to chain slip-
page or breakage. To prevent 
this from occurring, keep the 
drive chain slack within the 
specified limits. Drive chain length (15 
links):
<Limit>: 242.9 mm 
(9.563 in)
Drive chain lubricant:
SAE 10W-40 motor oil 
or suitable chain lubri-
cants
Drive chain slack:
50–60 mm (2.0–2.4 in)
To tighten→Turn the adjuster "3" 
counterclockwise.
To loosen→Turn the adjuster "3" 
clockwise and push wheel for-
ward. 
Page 68 of 196
3-18
CHASSIS
A. Right
B. Left
Turn the adjuster so that the drive 
chain is in line with the sprocket, as 
viewed from the rear.
d. Tighten the axle nut while pushing 
down the drive chain.
e. Tighten the locknuts.
CHECKING THE FRONT FORK
1. Inspect:
• Front fork smooth action
Operate the front brake and 
stroke the front fork.
Unsmooth action/oil leakage→
Repair or replace.
CHECKING THE FRONT FORK 
PROTECTOR GUIDE
1. Inspect:
• Protector guide "1"
Out of specification→Replacet.
The protector guide reaches the limit 
of its use when it is worn down to the 
same height "a" as of the outer tube 
circumference.
CLEANING THE FRONT FORK OIL 
SEAL AND DUST SEAL
1. Remove:
•Protector
• Dust seal "1"
Use a thin screw driver, and be care-
ful not to damage the inner fork tube 
and dust seal.
2. Clean:
• Dust seal "a"
• Oil seal "b"
• Clean the dust seal and oil seal af-
ter every run.
• Apply the lithium soap base grease 
on the inner tube.
RELIEVING THE FRONT FORK 
INTERNAL PRESSURE
If the front fork initial movement feels 
stiff during a run, relieve the front fork 
internal pressure.
1. Elevate the front wheel by placing 
a suitable stand under the engine.
2. Remove the air bleed screw "1" 
and release the internal pressure 
from the front fork.
3. Install:
• Air bleed screwADJUSTING THE FRONT FORK 
REBOUND DAMPING FORCE
1. Adjust:
• Rebound damping force
By turning the adjuster "1".
• STANDARD POSITION:
This is the position which is back 
by the specific number of clicks 
from the fully turned-in position.
Do not force the adjuster past the 
minimum or maximum extent of 
adjustment. The adjuster may be 
damaged.
Always adjust each front fork to 
the same setting. Uneven adjust-
ment can cause poor handling and 
loss of stability.
Axle nut:
135 Nm (13.5 m•kg, 98 
ft•lb)
Locknut:
21 Nm (2.1 m•kg, 15 
ft•lb)
Air bleed screw:
1 Nm (0.1 m•kg, 0.7 
ft•lb)
Stiffer "a" →Increase the re-
bound damping force. (Turn 
the adjuster "1" in.)
Softer "b" →Decrease the re-
bound damping force. (Turn 
the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in 
position20 clicks out 
(from maximum 
position)
Standard position:
10 clicks out
* 9 clicks out
* Except for USA and CDN 
Page 71 of 196
3-21
CHASSIS
CHECKING AND TIGHTENING THE 
SPOKES
The following procedure applies to all 
of the spokes.
1. Check:
• Spokes
Bend/damage→Replace.
Loose spoke→Retighten.
Tap the spokes with a screw-
driver.
A tight spoke will emit a clear, ringing 
tone; a loose spoke will sound flat.
2. Tighten:
• Spokes
(with a spoke nipple wrench "1")
Be sure to retighten these spokes be-
fore and after break-in.
CHECKING THE WHEELS
1. Inspect:
• Wheel runout
Elevate the wheel and turn it.
Abnormal runout→ Replace.2. Inspect:
• Bearing free play
Exist play→Replace.
CHECKING AND ADJUSTING THE 
STEERING HEAD
1. Place a stand under the engine to 
raise the front wheel off the 
ground. WARNING! Securely 
support the vehicle so that 
there is no danger of it falling 
over.
2. Check:
• Steering stem
Grasp the bottom of the forks and 
gently rock the fork assembly 
back and forth.
Free play→Adjust steering head.
3. Check:
• Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action→Adjust steer-
ing ring nut.
4. Adjust:
• Steering ring nut
Steering ring nut adjustment 
steps:
a. Remove the number plate.
b. Remove the handlebar and upper 
bracket.c. Loosen the steering ring nut "1" 
using the steering nut wrench "2".
d. Tighten the steering ring nut "3" 
using steering nut wrench "4".
• Apply the lithium soap base grease 
on the thread of the steering stem.
• Set the torque wrench to the steer-
ing nut wrench so that they form a 
right angle.
e. Loosen the steering ring nut one 
turn.
f. Retighten the steering ring nut us-
ing the steering nut wrench.
Avoid over-tightening.
g. Check the steering stem by turn-
ing it lock to lock. If there is any 
binding, remove the steering stem 
assembly and inspect the steer-
ing bearings. Spoke nipple wrench:
YM-01521/90980-01521
Spokes:
3 Nm (0.3 m•kg, 2.2 
ft•lb)
Steering nut wrench:
YU-33975/90890-01403
Steering nut wrench:
YU-33975/90890-01403
Steering ring nut (initial 
tightening):
38 Nm (3.8 m•kg, 27 
ft•lb)
Steering ring nut (final 
tightening):
7 Nm (0.7 m•kg, 5.1 
ft•lb) 
Page 74 of 196
3-24
ELECTRICAL
ELECTRICAL
CHECKING THE SPARK PLUG
1. Remove:
• Spark plug
2. Inspect:
• Electrode "1"
Wear/damage→Replace.
• Insulator color "2"
Normal condition is a medium to 
light tan color.
Distinctly different color→Check 
the engine condition.
When the engine runs for many hours 
at low speeds, the spark plug insula-
tor will become sooty, even if the en-
gine and carburetor are in good 
operating condition.
3. Measure:
• Plug gap "a"
Use a wire gauge or thickness 
gauge.
Out of specification→Regap.
4. Clean the plug with a spark plug 
cleaner if necessary.
5. Tighten:
• Spark plug
• Before installing a spark plug, clean 
the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug 
before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:
• Timing mark accessing screw "1"
2. Attach:
• Timing light
• Digital tachometer
To the ignition coil lead (orange 
lead"1").
3. Adjust:
• Engine idling speed
Refer to "ADJUSTING THE EN-
GINE IDLING SPEED" section.
4. Check:
• Ignition timing
Visually check the stationary 
pointer "a" is within the firing 
range "b" on the rotor.
Incorrect firing range→Check ro-
tor and pickup assembly.
5. Install:
• Timing mark accessing screw Spark plug gap:
0.7–0.8 mm 
(0.028–0.031 in)
Spark plug:
13 Nm (1.3 m•kg, 9.4 
ft•lb)
Timing light:
YM-33277-A/90890-
03141