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Mixture Control Valve Troubleshooting; Carburetor Air Vent System (california-only Models); Troubleshooting Hints; Common Causes Of Customer Complaints - Ducati 900SS Workshop Manual

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Table of Contents
I
No
paper reacti
on
I
I
Replace MCV
I
OK
Inspect
vacuum
lines
Assembly
1
and 3 way joont
instollatoo
n
Damage
I
R
eplace
vacuum
lines
I
Incorrec
t routi
ng
I
Route
correctly
I
I Contool
volve
2)
Coobuoetor
3)
Connislet
4)
Fuel tonk
0.62
I
CARBURETOR
Mixture
control valve
troubleshooting.
l
)Remove the
Mixture ConlroiVolve
{MC
V)
case
cover and
stort
the engine.
2)
Pioce
a
piece of
paper close
to
the
intake side
of the MCV.
3)Rev the
engine
to about
5000
rpm, and
quickly close
the
throttle.
The paper
should
be
drown
towards the
MCV
intake
.
Carburetor air vent system
(California-only
models).
All new
motorcycles
sold in
California
ore required to hove
on
emission cannister
in the
vent
lines running
from the
fuel
tonk and carburetors
.
This
is
to
prevent
the
discharging
of
fuel
vapors into
the
atmosphere.
Troubleshooting
hints.
1 )If it
is
difficult
to
set
or maintain carburetor synchronization, and
the
exhaust
gas
analyzer
show
s
a
leon
condition
exists
even
though
the
mixture
screw
has
been
enriched, check
for
on
air
leak
in the carburetor or
intake
manifold
.
Spray contact
cleaner on
the
supsected
point,
and watch
the CO
meter.
If
CO
increases, you've
found
the air
leak.
2)To check foro dogger or restricted
low-speed jet,
turn the
mixture
screw out {richer)
one full turn,
or more,
and watch
the
CO
needle. There
should
be
o
noticeable
increase
in
CO.
If
there
is
not,
the
low
-speed
jet
is
blocked.
3)A
common
complaint from
customers
is
that
the bike
hesitates
or
dies
when
the throlfle
is
opened
. The
carburetor
circuits
that
control
engine
speed
from
idle
to
midrange
ore
called transi
tion
circuits.
Transition
circuits ore
actually
a
combination
of
idle
and
midrange
circuits.
A
problem
with either
the
idle
or midrange carburetor
circui ts
or
on
ignition
problem,
con
cause
hesitation
or
missing
during
transition.
4)1f the exhaust
gas analyzer
readings
show
normal
CO
and
normal
HC,
but the bike
still hesitates off idle,
adjust
the
float levels
on
models
with
CV
carburetors.
5)0n those
models with
on
accelerator
pump,
olf·idle
hesitation con
usually be traced
to
on
improperly
adjusted
accelera tor
pump.
Use the
exhaust
gas
analyzer
to
adjust
the
accelerator
pump. Raise
the
engine
speed
to
5000
rpm,
hold
it
there
for
lwo
seconds, and
watch the
CO and
HC
meters.
If
the HC
needle
rises
before
the CO
needle, then
a
leon misfire
has
occurred
.
The
accelerator
pump
should
be
slightly
enrichened
(pump stroke
increased);
repeat
the
test.
Continue to enrichen
the accelerator
pump
and
test the
engine until
the
CO and
HC
needles rise
together;
the
leon misfire will
hove
been eliminated.
This
adjustment
will
yield smooth,
crisp
throHie
response.
COMMON CAUSES
OF
CUSTOMER COMPLAINTS
l
)Carburetors
not
properly
synchronized and exhaust
gas
analyzer' d
.
2)Excessively
rich
or
leon corburetion.
3)Ciogged
or restricted
internal
passages
.
4) Sticking fl
oats.
5) L eaki
ng
choke.
6)Worn
internal
ports
(jet needle,
needle jet,
float
valve)
.
7
)Dirty
or
obstructed
air
cleaner.
8)Air
leaks.
9)Molfunctiontng fuel subsystem.
1
0)
Exhaust
system
altered.
·
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