Carburettor Overhaul - General Information; Carburettors - Removal And Installation - Yamaha TDM850 User Manual

6 Carburettor overhaul -
general information
1 Poor engine performance, hesitation, hard
starting, stalling, flooding and backfiring are all
signs that major carburettor maintenance may be
required.
2 Keep in mind that many so-called carburettor
problems are really not carburettor problems at
all, but mechanical problems within the engine or
ignition system malfunctions. Try to establish for
certain that the carburettors are in need of
maintenance before beginning a major overhaul.
3 Check the fuel tap and filter, the fuel and
vacuum hoses, the intake manifold joint clamps,
the air filter, the ignition system, the spark plugs,
valve clearances and carburettor synchronisation
before assuming that a carburettor overhaul is
required.
4 Most carburettor problems are caused by dirt
particles, varnish and other deposits which build
up in and block the fuel and air passages,
especially if the motorcycle has been laid up for a
time. Also, in time, gaskets and O-rings shrink or
deteriorate and cause fuel and air leaks which
lead to poor performance.
5 When overhauling the
disassemble them completely and clean the parts
thoroughly with a carburettor cleaning solvent
and dry them with filtered,
compressed air. Blow through the fuel and air
passages 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, reassemble the carburettor
using new gaskets and O-rings.
6 Before disassembling the carburettors, make
sure you have all necessary O-rings and other
parts, some carburettor cleaner, a supply of clean
rags, some means of blowing out the carburettor
passages and a clean place to work. It is
recommended that only one carburettor be
overhauled at a time to avoid mixing up parts.
7.5a Detach the drain hoses (arrowed)...
7.2a Slacken the clamp screw (arrowed)...
carburettors,
7.4a Idle speed adjuster bolt (arrowed) -TDM
unlubricated
models
7 Carburettors -
removal and installation
A
Warning: Refer to the precautions
given in Section 1 before starting
work.
Removal
1 Remove the fuel tank and the air filter housing
(see Sections 2 and 4).
2 Slacken the choke outer cable bracket screw
and free the cable from the bracket on the front of
the carburettors, then detach the inner cable
nipple from the choke linkage lever (see
illustrations).
3 Detach the throttle
carburettors (see Section 11, Steps 2 and 3).
7.5b ... and the fuel hose
Fuel and exhaust systems 4»7
7.2b ... and detach the cable end from the
7.4b Idle speed adjuster bolt (arrowed) -TRX
If access is too restricted, detach them after the
^
carburettors have been lifted off the cylinder
«| head intakes.
4 On TDM and TRX models, unscrew the bolt
securing the idle speed adjuster and feed it
through to the base of the carburettors (see
illustrations).
5 Release the clamp securing the drain hose to
the bottom of each float chamber and detach the
hoses (see illustration). Also release the clamp
securing the fuel supply hose to the carburettors
and detach the hose (see illustration); be
careful to catch the small gauze filter fitted in the
fuel supply hose union as the hose is detached
(except 1999 TDM models).
6 On 1996-on TDM models and TRX models,
disconnect the wiring connector from the throttle
position sensor on the left-hand end of the
cables from the
carburettors (see illustration). Also
7.6 Disconnect the throttle position sensor
wiring connector (arrowed)
lever
models
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