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VI DEFECTS, CAUSES AND REMEDIES
Fault
Location
Remedy
Engine is pinking
Engine overheated
Plug point glow, faulty sparking plug (wrong
thermic grade)
Cylinder head clogged with carbon
Over-advanced ignition
Exhaust silencer clogged with carbon (esp. pipe)
Let engine cool off, do not run at high revolutions
Replace sparking plug
Remove head and decarbonise
Set ignition
Dismantle and clean exhaust silencer, & pipe
Regular spark
Water or oil in carburettor
Insufficient fuel supply
Temporary short circuit of lead against cylinder or
frame
Lean mixture
Incorrectly mixed petrol
Clean carburettor
Open tap completely (reserve), top up, check fuel
feed and filler cap breather hole
Tape crack in insulation, or, preferably replace lead
Clean jet, adjust carburettor
Stir mixture properly before re-fuelling
L
u
m
p
y
r
unning
E
ngine m
isfir
es
Irregular spark
Unsuitable sparking plug
Oiled sparking plug
Excessive sparking plug point gap
Soiled contact breaker points
Burnt contact breaker points
Incorrect contact breaker point gap
Faulty condenser, the ignition is out of function
Temporary short circuit of lead against cylinder or
frame
Replace sparking plug
Remove and clean sparking plug
Set gap to 0.5 mm by bending outer plug point
Clean points with cloth dipped in petrol
File with a fine file
Set gap to 0.4 mm
Replace condenser
Tape crack in insulation, or preferably, replace lead
Carburettor can be
flooded
Empty fuel tank
Fuel tap closed or insufficiently open
Turn fuel tap to open reserve (approx. 18 miles) and
refuel as soon as possible
Open fuel tap
Carburettor can not be
flooded
Clogged screen above fuel tap
Choked fuel feed or carburettor screen
Choked breathing hole in fuel tank filler cap
Remove fuel tap and clean screen
Remove feed and blow through. Remove carburettor
and clean jet
Clean breathing hole
Spark at
lead
end
Oiled sparking plug
Damaged plug insulation
Plug point gap either excessive or insufficient
Remove and clean plug
Replace plug
Set gap to 0.5 mm by bending outer plug point
No spar
k at spar
king plug points
No spark at lead
end
Switch box lever in incorrect position
Faulty ignition coil
Soiled contact breaker points
Burnt contact breaker points
Faulty contact breaker points
Switch box lead broken or loose
Burnt lead insulation
Faulty condenser
Damaged stator winding insulation
Water in contact breaker
Damaged bakelite lead terminal
Turn lever to correct position
Replace ignition coil
Wipe points with cloth dipped in petrol
File with fine file
Have contact breaker points repaired or replace
Replace lead, if impossible connect and insulate with
tape but replace soon
Tape lead, but replace lead as soon as possible
Replace condenser
Have magneto repaired
Blow water out, dry carefully or let dry
Replace terminal
Engine will not fire – engine has stopped
Car
bur
ettor
can be flooded
Spar
king
re
gular
Poor
co
m
p
-
ression
Seized piston ring
Broken piston ring
Leaking sparking plug washer
Damaged cylinder head gasket
Seized piston
Remove, clean and fit (or replace)
Remove ring and replace
Replace sparking plug washer
Seal with sealing compound
Dismantle and have repaired in specialised workshop
Carb-
urettor in
or
der
Engine overheated
Insufficient lubrication
Throttle cable broken
Faulty seal between carburettor and cylinder
Let engine cool off, keep it running at low revolutions
Take care to mix fuel mixture properly and at correct
ratio
Replace throttle cable
Replace seal or tighten carburettor stub
Engine will not start
or
has stopped
Car
bur
ettor
can be
floo
ded
Co
m
p
ression norm
a
l
Faulty
Carb-
urettor
Choked jet
Faulty float
Float stuck
Faulty float needle
Remove and clean jet
Have float repaired or replace
Free float
Repair or replace
Permanently
Cylinder head and barrel, exhaust port and exhaust
silencer clogged with carbon
Fuel feed partly choked
Incorrect ignition advance setting
Carburettor incorrectly set (bad mixture)
Throttle valve stuck
Clogged exhaust silencer
Cylinder inside and piston worn
Engine draws false air (damaged crankcase halves
or carburettor stub seal)
Brake shoes rub against drums
Remove cylinder head and barrel, if necessary
exhaust silencer and decarbonise
Remove and clean fuel feed
Set correct contact breaker point gap and ignition
advance
Set idling jet, needle position and clean air cleaner
Free and adjust throttle valve to work properly
Dismantle and decarbonise
Have cylinder rebored, replace piston and rings,
check piston bearing for wear (workshop)
Separate crankcase halves clean seating faces, insert
new paper gasket, compound & tighten fast. Replace
stub seal
Adjust brakes
E
ngine lacks power
Temporarily
Partly clogged fuel feed or screen in tap or carb.
Throttle cable sticks
Engine overheated
Faulty sparking plug
Clean fuel feed or screens
Lubricate cable, if necessary replace
Let engine cool off and keep at low revolutions
Replace plug
18 of 18
JAWA 50 type 20, 21, 23, 23A Owners Handbook page 63 to 68
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