User Guide

Chapter 3 Part A Fuel and exhaust systems (XV535 models)
3A-5
2.14a Remove the mounting bolts ... 2.14b ... and detach the rubber dampers
from the brackets
6.6 Free the hose from the retaining clips
Even after cleaning and flushing of the fuel system, explosive fumes
can remain and ignite during repair of the tank.
2 If the fuel tank is removed from the vehicle, it should not be
placed in an area where sparks or open flames could ignite the fumes
coming out of the tank. Be especially careful inside garages where a
natural gas-type appliance is located, because the pilot light could
cause an explosion.
4 Idle fuel/air mixture adjustment - general information
1 Due to the increased emphasis on controlling motorcycle exhaust
emissions, certain governmental regulations have been formulated
which directly affect the carburetion of this machine. In order to
comply with the regulations, the carburetors on some models have a
metal sealing plug pressed into the hole over the pilot screw (which
controls the idle fuel/air mixture) on each carburetor, so they can't be
tampered with. These should only be removed in the event of a
complete carburetor overhaul, and even then the screws should be
returned to their original settings. The pilot screws on other models are
accessible, but the use of an exhaust gas analyzer is the only accurate
way to adjust the idle fuel/air mixture and be sure the machine doesn't
exceed the emissions regulations.
2 If the engine runs extremely rough or blows black smoke at idle or
continually stalls, and if a carburetor overhaul does not cure the
problem, take the motorcycle to a Yamaha dealer service department
or other repair shop equipped with an exhaust gas analyzer. They will
be able to properly adjust the idle fuel/air mixture to achieve a smooth
idle and restore low speed performance.
5 Carburetor overhaul - general information
1 Poor engine performance, hesitation, hard starting, stalling,
flooding and backfiring are all signs that major carburetor maintenance
may be required.
2 Keep in mind that many so-called carburetor problems are really
not carburetor problems at all, but mechanical problems within the
engine or ignition system malfunctions. Try to establish for certain that
the carburetors are in need of maintenance before beginning a major
overhaul.
3 Check the fuel filter, the fuel lines, the fuel tank breather hose(s),
the rollover valve (models with evaporative emission control), the
intake manifold hose clamps, the vacuum hoses, the air filter element,
the cylinder compression, the spark plugs, the carburetor synchro-
nization and the fuel pump before assuming that a carburetor overhaul
is required.
4 Most carburetor problems are caused by dirt particles, varnish
and other deposits which build up in and block the fuel and air
passages. Also, in time, gaskets and O-rings shrink or deteriorate and
cause fuel and air leaks which lead to poor performance.
5 When the carburetor is overhauled, it is generally disassembled
completely and the parts are cleaned thoroughly with a carburetor
cleaning-solvent and dried with filtered, unlubricated compressed air.
The fuel and air passages are also blown through with compressed air
to force out any dirt that may have been loosened but not removed by
the solvent. Once the cleaning process is complete, the carburetor is
reassembled using new gaskets, O-rings and, generally, a new inlet
needle valve and seat.
6 Before disassembling the carburetors, make sure you have a
carburetor rebuild kit (which will include all necessary O-rings and
other parts), some carburetor cleaner, a supply of rags, some means of
blowing out the carburetor passages and a clean place to work. It is
recommended that only one carburetor be overhauled at a time to
avoid mixing up parts.
7 Don't separate the carburetors from each other unless one of the
joints between them is leaking. The carburetors can be overhauled
completely without being separated, and reconnecting them properly
can be difficult.
6 Carburetors and intake joints - removal and
installation
Warning: Gasoline (petrol) is extremely flammable, so take extra
precautions when you work on any part of the fuel system. Don't smoke
or allow open flames or bare light bulbs near the work area, and don't
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 an
extinguisher suitable for class B fires (flammable liquids) on hand.
Removal
Refer to illustrations 6.6, 6.8, 6.9, 6.10a, 6.10b, 6.11a, 6.11b, 6.11c,
6.13a and 6.13b
1 Remove the seat (see Chapter 7).
2 If you're working on a model with an upper fuel tank, remove it
(see Section 2).
3 If you're working on a model without an upper fuel tank, remove
the top cover (see Chapter 7).
4 Remove the left front side cover and its bracket (see Chapter 7).
5 . Remove the right front side cover and the electrical component
board beneath it (see Chapter 7).
6 Work the hose on the right side free of the clips (see illustration).
7 Disconnect the throttle cable from the pulley (see Section 9).