Haynes Yamaha Xv V Twins Manual

							
1-14 
Chapter 1 Tune-up and routine maintenance

12.3 Remove the filler plug to check final

drive oil level 
12.4a The oil should be even with the top

of the filler hole

12.4b Add oil through the filler hole

12.7a Remove the drain plug ,

12.7b ... and let the oil drain into a pan, then clean the plug

threads and reinstall it

3 Remove the filler plug from the final drive housing (see

illustration).

4 Look inside the hole and check the oil level. It should be even with

the top of the hole (see illustration). If its low, add oil of the type listed 
in this Chapters Specifications with a funnel or hose (see illustration),

then reinstall the filler plug and tighten it to the torque listed in this

Chapters Specifications.

Oil change

Refer to illustrations 12.7a and 12.7b

5 Ride the bike to warm the oil so it will drain completely. Warning:

Be careful not to touch hot components (including the oil); they may be

hot enough to cause burns.

6 Remove the filler plug (see illustration 12.3).

7 Remove the drain plug and let the oil drain for 10 to 15 minutes

(see illustrations).

8 Clean the drain plug, reinstall it and tighten it to the torque listed

in this Chapters Specifications.

9 Fill the final drive unit to the correct level with oil of the type listed

in this Chapters Specifications (see illustrations 12.4a and 12.4b).

10 Install the filler plug and tighten it to the torque listed in this

Chapters Specifications.

13 Engine oil/filter - change

Refer to illustrations 13.4a, 13.4b, 13.4c, 13.5a through 13.5c, 13.6a,

13.6b, 13.7 and 13.13

1 Consistent routine oil and filter changes are the single most

important maintenance procedure you can perform on a motorcycle.

The oil not only lubricates the internal parts of the engine, transmission

and clutch, but it also acts as a coolant, a cleaner, a sealant, and a

protectant. Because of these demands, the oil takes a terrific amount

of abuse and should be replaced Often with new oil of the

recommended grade and type. Saving a little money on the difference

in cost between a good oil and a cheap oil wont pay off if the engine is

damaged.

2 Before changing the oil and filter, warm up the engine so the oil

will drain easily. Be careful when draining the oil, as the exhaust pipes,

the engine, and the oil itself can cause severe burns.

3 Support the motorcycle securely over a clean drain pan. Remove

the oil filler cap to vent the crankcase and act as a reminder that there

is no oil in the engine.

4 Next, remove the drain plug from the engine (see illustrations)

and allow the oil to drain into the pan (see illustration). Discard the

sealing washer on the drain plug; it should be replaced whenever the

plug is removed.

5 Remove the Allen bolts and take off the filter cover (see

illustrations).

6 Remove the filter element from the engine (see illustrations). 
						

							
Chapter 1 Tune-up and routine maintenance

1-15

13.4a The oil drain plug (arrow) is located

on the left side of the engine (XV535

shown; others similar) 
13.4b Loosen the drain plug with

a socket... 
13.4c ... and let the oil drain into a pan

13.5a On XV535 models, remove the Allen

bolts (arrows) ... 
13.5b ... and remove the cover

13.5c On XV700 through 1100 models,

remove the Allen bolts (arrows)...

13.6a ... and remove the cover together

with its two O-rings 
13.6b Pull the filter element out of

the engine 
13.7 On XV535 models, remove the 0-

ring from the groove in the cover 
						

							
1-16 
Chapter 1 Tune-up and routine maintenance

13.13 Make sure the washer is in position

on the inner end of the filter element 
14.2 Remove the screw (1), then lift the

housing cover

14.5a Remove the case cover

bolts (arrows)...

14.5b ... be careful not to lose the spacer tubes and washers

7 If youre working on an XV535 model, remove the O-ring from its

groove in the cover (see illustration).

8 If youre working on an XV700 through 1100 model, remove one

O-ring from the groove in the cover and another from the shoulder on

the cover (see illustration 13.6a).

9 Clean the filter cover and housing with solvent or clean rags.

Make sure the holes in the filter bolt are clear. Wipe any remaining oil

off the filter sealing area of the crankcase.

10 Clean the components and check them for damage. If any

damage is found, replace the damaged part(s).

11 Check the condition of the drain plug threads and the sealing

washer.

12 Install a new O-ring in the cover groove (XV535) or in the groove

and against the cover shoulder (XV700-1100) (see illustration 13.6a or

13.7).

13 Make sure the rubber seal is in place (see illustration), then

install the filter element in the cover. Install the cover on the engine and

tighten the Allen bolts to the torque listed in this Chapters Specifi-

catidns.

14 Slip a new sealing washer over the crankcase drain plug, then

install and tighten it to the torque listed in this Chapters Specifi-

cations. Avoid overtightening, as damage to the engine case will result.

15 Before refilling the engine, check the old oil carefully. If the oil was

drained into a clean pan, small pieces of metal or other material can be 
easily detected. If the oil is very metallic colored, then the engine is

experiencing wear from break-in (new engine) or from insufficient

lubrication. If there are flakes or chips of metal in the oil, then

something is drastically wrong internally and the engine will have to be

disassembled for inspection and repair.

16 If there are pieces of fiber-like material in the oil, the clutch is

experiencing excessive wear and should be checked.

17 If the inspection of the oil turns up nothing unusual, refill the

crankcase to the proper level with the recommended oil and install the

filler cap. Start the engine and let it run for two or three minutes. Shut it

off, wait a few minutes, then check the oil level. If necessary, add more

oil to bring the level up to the Maximum mark. Check around the drain

plug and filter housing for leaks.

18 The old oil drained from the engine cannot be reused in its

present state and should be disposed of. Check with your local refuse

disposal company, disposal facility or environmental agency to see

whether they will accept the used oil for recycling. Dont pour used oil

into drains or onto the ground. After the oil has cooled, it can be

drained into a suitable container (capped plastic jugs, topped bottles,

milk cartons, etc.) for transport to one of these disposal sites.

14 Air filter element - servicing

XV535 models

Refer to illustration 14.2

1 Remove the top cover (see Chapter 7) or upper fuel tank (see

Chapter 3).

2 Remove the cover screw and lift off the housing cover (see

illustration). Inspect the cover O-ring and replace it if its damaged or

deteriorated.

3 Lift out the filter element.

1981 through 1983 and all TR1 models

Refer to illustrations 14.5a, 14.5b, 14.6, 14.7a and 14.7b

4 Remove the left side cover (see Chapter 7).

5 Remove the Allen bolts and detach the air filter housing from the

motorcycle (see illustrations).

6 Lay the housing on a workbench. Remove the screws that hold

the halves of the assembly together, then separate them and lift out

the element (see illustration).

7 Check the filter housing-to-frame seal and the seals inside the

filter housing for deterioration or brittleness (see illustrations).

Replace the seals as necessary. 
						

							
Chapter 1 Tune-up and routine maintenance

1-17

14.6 Separate the housing halves and

take the filter element out 
14.7a Check the seal between the filter

housing and the frame ... 
14.7b ... and the seals inside the filter

housing; replace them if theyre

deteriorated or brittle

14.9 Loosen the clamp bolt and remove

the Allen bolts, then detach the air filter

case from the motorcycle 
14.10a Remove the cover from the inside

of the case 
14.10b Remove the filter element

retaining screw, detach the mounting tab

and lift out the element

1984 and later XV700 through 1100 models

Refer to illustrations 14.9, 14.10a and 14.10b

8 Remove the fuel tank (see Chapter 3).

9 Loosen the air duct clamp bolt and remove the mounting bolts,

then take the air filter case off the motorcycle (see illustration).

10 Remove the air filter case cover (see illustration). Remove the

element mounting screw and take the element out (see illustration).

All models

11 Tap the element on a hard surface to shake out dirt. If

compressed air is available, use it to clean the element by blowing

from the inside out. If the element is extremely dirty or torn, or if dirt

cant be blown or tapped out, replace it with a new one.

12 Reinstall the filter by reversing the removal procedure. Make sure

the element is seated properly in the filter housing before installing the

cover.

13 Install all components removed for access.

15 Cylinder compression - check

1 Among other things, poor engine performance may be caused by

leaking valves, incorrect valve clearances, a leaking head gasket, or

worn pistons, rings and/or cylinder walls. A cylinder compression

check will help pinpoint these conditions and can also indicate the

presence of excessive carbon deposits in the cylinder heads.

2 The only tools required are a compression gauge and a spark 
plug wrench. Depending on the outcome of the initial test, a squirt-

type oil can may also be needed.

3 Start the engine and allow it to reach normal operating

temperature.

4 Support the bike securely so it cant be knocked over during this

procedure.

5 Remove the spark plugs (see Section 16, if necessary). Work

carefully - dont strip the spark plug hole threads and dont burn your

hands.

6 Disable the ignition by unplugging the primary wires from the coils

(see Chapter 4). Be sure to mark the locations of the wires before

detaching them.

7 Install the compression gauge in one of the spark plug holes.

8 Hold or block the throttle wide open.

9 Crank the engine over a minimum of four or five revolutions (or

until the gauge reading stops increasing) and observe the initial

movement of the compression gauge needle as well as the final total

gauge reading. Repeat the procedure for the other cylinder and

compare the results to the value listed in this Chapters Specifications.

10 If the compression in both cylinders built up quickly and evenly to

the specified amount, you can assume the engine upper end is in

reasonably good mechanical condition. Worn or sticking piston rings

and worn cylinders will produce very little initial movement of the

gauge needle, but compression will tend to build up gradually as the

engine spins over. Valve and valve seat leakage, or head gasket

leakage, is indicated by low initial compression which does not tend to

build up.

11 To further confirm your findings, add a small amount of engine oil 
						

							
1-18 
Chapter 1 Tune-up and routine maintenance

16.2 On XV535 models, remove the Allen

bolts and lift off the cylinder head

side covers 
16.3b ... check the rubber seals for

brittleness and the plastic for cracks

16.3c The spark plugs are inside wells in

the cylinder heads, so youll need a

socket with a rubber insert to grip

the plug 
16.7a Spark plug manufacturers

recommend using a wire type gauge when

checking the gap - if the wire doesnt slide

between the electrodes with a slight drag,

adjustment is required 
16.7b To change the gap, bend the side

electrode only, as indicated by the

arrows, and be very careful not to crack

or chip the ceramic insulator surrounding

the center electrode

to each cylinder by inserting the nozzle of a squirt-type oil can through

the spark plug holes. The oil will tend to seal the piston rings if they are

leaking. Repeat the test for the other cylinder.

12 If the compression increases significantly after the addition of the

oil, the piston rings and/or cylinders are definitely worn. If the

compression does not increase, the pressure is leaking past the valves

or the head gasket. Leakage past the valves may be due to insufficient

valve clearances, burned, warped or cracked valves or valve seats or

valves that are hanging up in the guides.

13 If compression readings are considerably higher than specified,

the combustion chambers are probably coated with excessive carbon

deposits. It is possible (but not very likely) for carbon deposits to raise

the compression enough to compensate for the effects of leakage past

rings or valves. Remove the cylinder head and carefully decarbonize

the combustion chambers (see Chapter 2).

16 Spark plugs - replacement

Refer to illustrations 16.2, 16.3a, 16.3b, 16.3c, 16.7aand 16.7b

1 Make sure your spark plug socket is the correct size before

attempting to remove the plugs.

2 If youre working on an XV535 model, remove the cylinder head

side covers (see illustration). 
3 Disconnect the spark plug caps from the spark plugs (see

illustrations). If available, use compressed air to. blow any

accumulated debris from around the spark plugs. Remove the plugs

(see illustration).

4 Inspect the electrodes for wear. Both the center and side

electrodes should have square edges and the side electrode should be

of uniform thickness. Look for excessive deposits and evidence of a

cracked or chipped insulator around the center electrode. Compare

your spark plugs to the color spark plug reading chart. Check the

threads, the washer and the ceramic insulator body for cracks and

other damage.

5 If the electrodes are not excessively worn, and if the deposits can

be easily removed with a wire brush, the plugs can be regapped and

reused (if no cracks or chips are visible in the insulator). If in doubt

concerning the condition of the plugs, replace them with new ones, as

the expense is minimal.

6 Cleaning spark plugs by sandblasting is permitted, provided you

clean the plugs with a high flash-point solvent afterwards.

7 Before installing new plugs, make sure they are the correct type

and heat range. Check the gap between the electrodes, as they are not

preset. For best results, use a wire-type gauge rather than a flat gauge

to cheGk the gap (see illustration). If the gap must be adjusted, bend

the side electrode only and be very careful not to chip or crack the

insulator nose (see illustration). Make sure the washer is in place

before installing each plug.
16.3a Twist and pull the spark plug caps

to detach them from the plugs ... 
						

							
For a COLOR version of this spark plug diagnosis page, please see the inside rear cover of this manual

CARBON DEPOSITS

Symptoms: Dry sooty deposits

indicate a rich mixture or weak

ignition. Causes misfiring, hard

starting and hesitation.

Recommendation: Check for

a clogged air cleaner, high float

level, sticky choke and worn ig-

nition points. Use a spark plug

with a longer core nose for

greater anti-fouling protection.

OIL DEPOSITS

Symptoms: Oily coating

caused by poor oil control. Oil

is leaking past worn valve

guides or piston rings into the

combustion chamber. Causes

hard starting, misfiring and

hesition.

Recommendation: Correct

the mechanical condition with

necessary repairs and install

new plugs.

TOO HOT

Symptoms: Blistered, white in-

sulator, eroded electrode and

absence of deposits. Results in

shortened plug life.

Recommendation: Check for

the correct plug heat range,

over-advanced ignition timing,

lean fuel mixture, intake mani-

fold vacuum leaks and sticking

valves. Check the coolant level

and make sure the radiator is

not clogged.

HIGH SPEED GLAZING

Symptoms: Insulator has

yellowish, glazed appearance.

Indicates that combustion

chamber temperatures have

risen suddenly during hard ac-

celeration. Normal deposits

melt to form a conductive coat-

ing. Causes misfiring at high

speeds.

Recommendation: Install new

plugs. Consider using a colder

plug if driving habits warrant. 
NORMAL

Symptoms: Brown to grayish-

tan color and slight electrode

wear. Correct heat range for

engine and operating condi-

tions.

Recommendation: When new

spark plugs are installed, re-

place with plugs of the same

heat range.

ASH DEPOSITS

Symptoms: Light brown de-

posits encrusted on the side or

center electrodes or both. De-

rived from oil and/or fuel addi-

tives. Excessive amounts may

mask the spark, causing misfir-

ing and hesitation during accel-

eration.

Recommendation: If exces-

sive deposits accumulate over

a short time or low mileage, in-

stall new valve guide seals to

prevent seepage of oil into the

combustion chambers. Also try

changing gasoline brands.

DETONATION

Symptoms: Insulators may be

cracked or chipped. Improper

gap setting techniques can

also result in a fractured insu-

lator tip. Can lead to piston

damage.

Recommendation: Make sure

the fuel anti-knock values meet

engine requirements. Use care

when setting the gaps on new

plugs. Avoid lugging the en-

gine.
PREIGNITION

Symptoms: Melted electrodes.

Insulators are white, but may

be dirty due to misfiring or fly-

ing debris in the combustion

chamber. Can lead to engine

damage.

Recommendation: Check for

the correct plug heat range,

over-advanced ignition timing,

lean fuel mixture, clogged cool-

ing system and lack of lubri-

cation.

GAP BRIDGING

Symptoms: Combustion de-

posits lodge between the elec-

trodes. Heavy deposits accu-

mulate and bridge the elec-

trode gap. The plug ceases to

fire, resulting in a dead cyl-

inder.

Recommendation: Locate the

faulty plug and remove the de-

posits from between the elec-

trodes. 
SPLASHED DEPOSITS

Symptoms: After long periods

of misfiring, deposits can

loosen when normal combus-

tion temperature is restored by

an overdue tune-up. At high

speeds, deposits flake off the

piston and are thrown against

the hot insulator, causing mis-

firing.

Recommendation: Replace

the plugs with new ones or

clean and reinstall the orig-

inals.

MECHANICAL DAMAGE

Symptoms: May be caused by

a foreign object in the combus-

tion chamber or the piston

striking an incorrect reach (too

long) plug. Causes a dead cyl-

inder and could result in piston

damage.

Recommendation: Remove

the foreign object from the en-

gine and/or install the correct

reach plug.
WORN

Symptoms: Rounded elec-

trodes with a small amount of

deposits on the firing end. Nor-

mal color. Causes hard starting

in damp or cold weather and

poor fuel economy.

Recommendation: Replace

with new plugs of the same

heat range. 
						

							
1-20 
Chapter 1 Tune-up and routine maintenance

17.2a Lubricate the brake pedal pivot... 
17.2b ... the footpeg and shift linkage

pivots (arrows) - XV1100 shown ... 
17.2c ... and the brake and clutch lever

pivots (brake lever shown; clutch

lever similar)

17.3a Lubricating a cable with a pressure lube adapter (make

sure the tool seats around the inner cable)

17.3b Oiling a control cable with a funnel
8 Since the cylinder head is made of aluminum, which is soft and

easily damaged, thread the plugs into the heads by hand. Since the

plugs are recessed, slip a short length of hose over the end of the plug

to use as a tool to thread it into place. The hose will grip the plug well

enough to turn it, but will start to slip if the plug begins to cross-thread

in the hole - this will prevent damaged threads and the accompanying

repair costs.

9 Once the plugs are finger tight, the job can be finished with a

socket. If a torque wrench is available, tighten the spark plugs to the

torque listed in this Chapters Specifications. If you do not have a

torque wrench, tighten the plugs finger tight (until the washers bottom

on the cylinder head) then use a wrench to tighten them an additional

1/4 to 1/2 turn. Regardless of the method used, do not over-tighten

them.

10 Reconnect the spark plug caps and reinstall the air ducts.

17 Lubrication - general

Refer to illustrations 17.2a, 17.2b, 17.2c, 17.3a and 17.3b

1 Since the controls, cables and various other components of a

motorcycle are exposed to the elements, they should be lubricated

periodically to ensure safe and trouble-free operation.

2 The footpegs, clutch and brake lever, brake pedal, shift lever and

sidestand/centerstand pivots should be lubricated frequently (see

illustrations). In order for the lubricant to be applied where it will do

the most good, the component should be disassembled. However, if

chain and cable lubricant is being used, it can be applied to the pivot 
joint gaps and will usually work its way into the areas where friction

occurs. If motor oil or light grease is being used, apply it sparingly as it

may attract dirt (which could cause the controls to bind or wear at an

accelerated rate). Note: One of the best lubricants for the control lever

pivots is a dry-film lubricant (available from many sources by different

names).

3 To lubricate the throttle and choke cables, disconnect the cable(s)

at the lower end, then lubricate the cable with a pressure lube adapter

(see illustration). If you dont have one, disconnect both ends of the

cable and use a funnel (see illustration). See Chapter 3, Part B for the

choke cable removal procedure (XV535 models dont have a choke

cable). Note: Yamaha recommends that the throttle twist grip be 
						

							
Chapter 1 Tune-up and routine maintenance

1-21

18.7a Remove the cover

bolts (arrows)... 
18.7b ... and lift the cover off 
18.8 Unscrew the timing plug (upper

arrow) and the crankcase cover plate

(lower arrow)

18.9a The timing mark for the rear cylinder is the line next to

the T on the alternator rotor; align it with the notch inside

the hole (arrow)

removed and lubricated whenever the throttle cables are lubricated.

Refer to the handlebar switch removal section of Chapter 8.

4 The speedometer cable should be removed from its housing and

lubricated with motor oil or cable lubricant.

5 Refer to Chapter 5 for the swingarm needle bearing and rear

suspension linkage lubrication procedures.

18 Valve clearances - check and adjustment

1 The engine must be completely cool for this maintenance

procedure, so let the machine sit overnight before beginning.

2 Disconnect the cable from the negative terminal of the battery.

Remove the spark plugs (see Section 16) so the crankshaft is easier to

turn.

3 Lift or remove the seat (see Chapter 7).

XV535 models

Refer to illustrations 18.7a, 18.7b, 18.8, 18.9a, 18.9b, 18.11 and 18.14

4 If youre working on an early model without an upper fuel tank,

remove the top cover (see Chapter 7).

5 If youre working on a later model with an upper fuel tank, remove

it (see Chapter 3).

6 Remove the left and right front side cover (see Chapter 3).

Remove the left side cover bracket and the left side cover

bracket/electrical component board.

7 Remove the rocker covers (see illustrations).

8 Remove the timing plug and the crankcase cover plate (see

illustration). 
18.9b XV535 timing marks

1 Rear cylinder top dead center mark

2 Frornt cylinder firing range mark

3 Front cylinder top dead center mark

18.11 Measure valve clearance with a feeler gauge; hold the

locknut with a box wrench (ring spanner) and turn the adjusting

screw with an Allen wrench or screwdriver

9 Turn the crankshaft clockwise with a socket on the turning bolt

(located inside the crankcase cover plate). Watch the edge of the

alternator rotor (visible through the timing plug hole) and stop turning

when the line next to the T mark is aligned with the notch inside the

hole (see illustrations). This places the rear cylinder at top dead

center (TDC) on its compression stroke.

10 With the engine in this position, both of the valves for the rear

cylinder can be checked.

11 Start with the intake valve clearance. Insert a feeler gauge of the

thickness listed in this Chapters Specifications between the rocker

arm and valve stem (see illustration). Pull the feeler gauge out slowly - 
						

							
1-22

Chapter 1 Tune-up and routine maintenance

18.14 The single line on the edge of the

alternator rotor is the top dead center

mark for the front cylinder 
18.22 Lift off the rocker cover

18.23 Remove the crankcase outer cover

18.24a The timing mark for the rear cylinder is the line next to the

T on the alternator rotor; align it with the pointer inside the hole 
18.24b XV700 through 1100 timing marks

1 Rear cylinder top dead center mark

2 Front cylinder top dead center mark

3 Rear cylinder firing range mark

you should feel a slight drag. If theres no drag, the clearance is too

loose. If theres a heavy drag, the clearance is too tight.

12 To adjust the clearance, loosen the rocker arm locknut with a box

wrench (ring spanner) (see illustration 18.11). Turn the adjusting

screw with a screwdriver or Allen wrench to change the clearance,

then tighten the locknut.

13 Recheck the clearance with the feeler gauge to make sure it didnt

change when you tightened the locknut. Readjust it if necessary.

14 Turn the engine clockwise to align the front cylinders timing mark

with the notch in the timing window (see illustration 18.9b and the

accompanying illustration). With the timing mark aligned, wiggle the

front cylinders rocker arms. There should be a slight amount of

cleararjjje between the rocker arms and valve stems. If the rocker arms

are tight,- the front piston is on its exhaust stroke, not its compression

stroke. Rotate the crankshaft one full turn, line up the timing mark

again, then wiggle the rocker arms to be sure the front cylinder is on

the compression stroke.

15 Perform Steps 11 through 13 above on the front cylinder rocker

arms to adjust the front cylinders valve clearances.

16 Check the O-rings on the rocker covers, timing plug and

crankcase cover plate and replace them if theyre flattened, broken or

have been leaking.

17 install the rocker covers and tighten their bolts to the torque listed

in this Chapters Specifications.

18 Install all components removed for access. 
XV700 through 1000 models

Refer to illustrations 18.22, 18.23, 18.24a and 18.24b

19 Remove the seat (see Chapter 7) and the fuel tank (see Chapter

3)-

20 If youre working on a 1981 through 1983 model, remove the side

covers if they block access to the tappet covers.

21 If youre working on a 1984 or later model, remove the air filter

housing (see Section 14) and the mixture control valve case (see

Chapter 3).

22 Remove the rocker covers (see illustration).

23 Remove the alternator cover from the left side of the engine (see

illustration).

24 Turn the crankshaft clockwise with a socket on the turning bolt

(located inside the crankcase cover plate). Watch the edge of the

alternator rotor (visible through the timing plug hole) and stop turning

when the line next to the T mark is aligned with the pointer inside the

hole (see illustrations). This places the rear cylinder at top dead

center (TDC) on its compression stroke.

25 Perform Steps 10 through 15 above to adjust the valve clearances

on both cylinders.

26 Check the O-rings on the rocker covers and alternator cover and

replace them if theyre flattened, broken or have been leaking.

27 Install the rocker covers and tighten their bolts to the torque listed

in this Chapters Specifications.

28 Install all components removed for access.

19 Idle speed - check and adjustment

Refer to illustration 19.3

1 The idle speed should be checked and adjusted before and after

the carburetors are synchronized and when it is obviously too high or

too low. Before adjusting the idle speed, make sure the valve

clearances and spark plug gaps are correct. Also, turn the handlebars 
						

							
Chapter 1 Tune-up and routine maintenance

1-23

19.3 Turn the throttle stop screw to set

idle speed (1981 through 1987 XV700

through 1100 shown; XV535 and 1988-on

XV750 and 1100 similar) 
20.7 Remove the rubber caps and connect

the vacuum gauges or manometer to the

fittings (A); turn the synchronizing screw

(B) to obtain even vacuum readings (XV535

shown; others similar) 
20.9 Disconnect the smaller ho^e from

the front carburetors intake joint and

connect one of the vacuum gauges or

manometer tubes to the fitting

back-and-forth and see if the idle speed changes as this is done. If it

does, the accelerator cable may not be adjusted correctly, or it may be

worn out. This is a dangerous condition that can cause loss of control

of the bike. Be sure to correct this problem before proceeding.

2 The engine should be at normal operating temperature, which is

usually reached after 10 to 15 minutes of stop and go riding. Support

the motorcycle securely and make sure the transmission is in Neutral.

3 Turn the throttle stop screw (see illustration), until the idle speed

listed in this Chapters Specifications is obtained.

4 Snap the throttle open and shut a few times, then recheck the idle

speed. If necessary, repeat the adjustment procedure.

5 If a smooth, steady idle cant be achieved, the fuel/air mixture

may be incorrect. Refer to Chapter 5 for additional carburetor

information.

20 Carburetor synchronization - check and adjustment

Warning: Gasoline is extremely flammable, so take extra precautions

when you work on any part of the fuel system. Dont smoke or allow

open flames or bare light bulbs near the work area, and dont work in a

garage where a natural gas-type appliance (such as a water heater or

clothes dryer) is present. If you spill any fuel on your skin, rinse it off

immediately with soap and water. When you perform any kind of work

on the fuel system, wear safety glasses and have a class B type fire

extinguisher on hand.

1 Carburetor synchronization is simply the process of adjusting the

carburetors so they pass the same amount of fuel/air mixture to each

cylinder. This is done by measuring the vacuum produced in each

cylinder. Carburetors that are out of synchronization will result in

decreased fuel mileage, increased engine temperature, less than ideal

throttle response and higher vibration levels.

2 To properly synchronize the carburetors, you will need some sort

of vacuum gauge setup, preferably with a gauge for each cylinder, or a

mercury manometer, which is a calibrated tube arrangement that

utilizes columns of mercury to indicate engine vacuum. Youll also

need an auxiliary fuel tank, since the bikes fuel tank must be removed

for access to the vacuum fittings and synchronizing screws.

3 A manometer can be purchased from a motorcycle dealer or

accessory shop and should have the necessary rubber hoses supplied

with it for hooking into the vacuum hose fittings on the carburetors.

4 A vacuum gauge setup can also be purchased from a dealer or

fabricated from commonly available hardware and automotive vacuum

gauges.

5 The manometer is the more reliable and accurate instrument, and

for that reason is preferred over the vacuum gauge setup; however,

since the mercury used in the manometer is a liquid, and extremely

toxic, extra precautions must be taken during useand storage of 
the instrument.

6 Because of the nature of the synchronization procedure and the

need for special instruments, most owners leave the task to a dealer

service department or a reputable motorcycle repair shop.

XV535 models

Refer to illustration 20.7

7 Remove the vacuum caps from the intake joint fittings (see

illustration). Connect the vacuum gauges or manometer to the fittings.

1981 through 1983 models

Refer to illustration 20.9

8 Remove the seat (see Chapter 7). If necessary for access, detach

the fuel tank and raise it slightly, leaving the fuel hoses connected (see

Chapter 3).

9 Disconnect the smaller hose from the front carburetors intake

joint (see illustration). Remove the rubber cap from the vacuym fitting

on the rear carburetors intake joint, then connect the vacuum gauges

or manometer to the hose fitting and vacuum fitting.

1984 through 1987 XV700 models

10 Remove the seat (see Chapter 7). Detach the fuel tank at the rear

and raise it slightly, leaving the fuel hoses connected..

11 Turn the fuel tap to the PRI position.

12 Disconnect the smaller hose from the front carburetors intake

joint (see illustration 20.9). Remove the rubber cap from the vacuum

fitting on the rear carburetors intake joint, then connect the vacuum

gauges or manometer to the hose fitting and vacuum fitting.

1984 through 1987 XV1000 and 1100 models

13 Remove the seat (see Chapter 7).

14 Remove the mixture control valve case cover (see Chapter 3).

Disconnect the mixture control valve vacuum hose at the T-fitting and

connect one of the manometer tubes or vacuum gauges to the fitting.

15 Remove the rubber cap from the vacuum fitting o%_tbe rear

carburetors intake joint and connect the other vacuurrNgauge or

manometer tube to it.

1988 and later models

16 Remove the seat (see Chapter 7) and the fuel tank (see Chap-

ter 3). Connect an auxiliary fuel source.

17 If youre working on an 1100 model, remove the left side cover.

18 Disconnect the smaller hose from the front carburetors intake

joint. Remove the rubber cap from the vacuum fitting on the rear

carburetors intake joint, then connect the vacuum gauges or

manometer to the hose fitting and vacuum fitting.