Zundapp 281 - Page 48

Troubles, and their Causes
1. Engine will not start
Cause: Fuel tap not opened, star-
ter aid not operated when starting
from cold. Jets clogged. Carburettor
flooded (engine drowned). Ignition
not switched on. Spark plug defec-
tive, spark too weak. Spark (elec-
trode) gap on plug too large, spark
plug short-circuited, gap clogged by
dirt water or oil.
2. Engine chokes back on starting
Cause: Ignition timing set too early
3. Engine starts badly
Cause: Mixture too lean (operate
starting aid). Idling jet clogged.
Spark plug dirty or oily; spark gap
too large or too small (weak spark).
Water in fuel.
4. Engine starts, but stops again after
short run
Cause: Carburettor empty, because
fuel tap remained closed
5. Engine starts, but stops on throttling
up
Cause: Main jet or fuel line clogged,
engine still too cold, carburettor
badly adjusted.
6.
Engine
starts,
but
carburettor
“spits
back”
on
throttling
up
(coughs
and
sneezes)
Cause: engine very cold, fuel mix-
ture
too
lean.
Jet
too
small
or
clog-
ged. Carburettor badly adjusted
(poor transitions). Too many late
firings.
Suction
intake
line
leaks
or
air
enters
at
carburettor
union,
. Engine starts, but runs irregularly
and splutters on throttling up
Cause: Mixture too rich (fit smaller
jets, alter needle setting of throttle
slide). Air filter dirty. Float over-
flows. Ignition cuts out. Spark plug
oily or coked up. Starter piston not
completely closed (high fuel con-
sumption).
. Engine runs properly, but exhaust
backfires
Cause: Ignition cuts out. Mixture too
lean,
. Engine knocks or pinks
Cause: Too many early firings, fuel
is not of anti-knock grade. Exces-
sive compression. Glowing coke de-
posits or parts of overheated spark
plug produce faulty ignition. Main
jet too small.
Engine does not pull or does not
give full performance
Cause: Mixture too lean or too rich.
Too few early firings. Exhaust clog-
ged. Piston leaks. Intake or exhaust
ports clogged by coking deposits,
Air filter dirty. Brakes drag. Fric-
tion losses in transmission compo-
nents,
. Float overflows
Cause: Foreign body carried in fuel
to float needle seat and obstructs
needle operation. Float leaks. Float
needle jumped out of float spring
or was wrongly mounted.