Cobra Moto CX50 BW 2010 User manual

For parts orders contact your local dealer
To locate your closest Cobra dealer
log on to
www.cobramotorcycle.com
or call
[phone]
If you need technical assistance
contact your local dealer or call
the Cobra Technical Support Hotline at
[phone]
Cobra Motorcycle MFG., Inc.
240 Uran Street
Hillsdale, Michigan 49242

DISCLAIMER OF WARRANTY
This motorcycle is sold “as is” with all faults, obvious or not. There are no warranties
expressed or implied, including any warranty of merchantability and warranty of fitness
for any particular purpose.
“WARNING”
THE COBRA CX50SR (KING) IS A COMPETITION MODEL ONLY AND IS NOT
MANUFACTURED FOR, NOR SHOULD IT BE USED ON PUBLIC STREETS, ROADS
OR HIGHWAYS.
THE USE OF THIS BIKE SHOULD BE LIMITED TO PARTICIPATION IN
SANCTIONED COMPETITION EVENTS UPON A CLOSED COURSE BY A
SUFFICIENTLY SKILLED RIDER AND SHOULD NOT BE USED FOR GENERAL
OFF-ROAD RECREATIONAL RIDING.
IMPROPER USE OF THIS MOTORCYCLE CAN CAUSE INJURY OR DEATH.
THIS BIKE IS INTENDED FOR EXPERIENCED RACERS ONLY AND NOT FOR
BEGINNERS.
IT IS YOUR RESPONSIBILITY AS THE OWNER OF THIS COBRA MOTORCYCLE
OR AS THE PARENT, OR LEGAL GUARDIAN OF THE OPERATOR, TO KEEP THIS
COBRA MOTORCYCLE IN PROPER OPERATING CONDITION.
THIS BIKE WAS DESIGNED FOR RIDERS THAT WEIGH LESS THAN 80 LBS WITH
FULL RIDING GEAR AND SHOULD NOT BE OPERATED BY RIDERS THAT WEIGH
MORE THAN THAT.
BE SURE THAT THE RIDER ALWAYS WEARS ADEQUATE SAFETY GEAR
EVERYTIME HE OR SHE RIDES THEIR COBRA MOTORCYCLE.
IMPORTANT SAFETY NOTICE
Failure to follow WARNING instructions could result in severe injury or death to
the machine operator, a bystander, or a person inspecting or repairing the
machine.
CAUTION:
A CAUTION indicates special precautions that must be taken to avoid damage to
the machine.
NOTE:
A NOTE provides key information to make procedures easier or clearer.
MCCS2010.1

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Table Of Contents
GENERAL INFORMATION...................................................................................5
SPECIFICATIONS - GENERAL.................................................................................5
OPTIONAL COMPONENTS......................................................................................6
SPECIFICATIONS - TORQUE VALUES ......................................................................6
BREAK-IN PROCEDURE.........................................................................................8
STARTING PROCEDURE........................................................................................9
MAINTENANCE..................................................................................................10
TIPS .................................................................................................................10
SCHEDULE ........................................................................................................11
REPLACING TRANSMISSION / CLUTCH LUBRICANT.................................................12
PROPER CHAIN ADJUSTMENT..............................................................................14
REAR BRAKE MAINTENANCE...............................................................................14
AIR FILTER CLEANING ........................................................................................16
FORK OIL REPLACEMENT ...................................................................................19
FRICTIONAL DRIVE (CFD) ..................................................................................20
PARTS................................................................................................................21
PARTS – AIRBOX & INLET SYSTEM......................................................................21
PARTS – BARS AND CONTROLS ..........................................................................22
PARTS - CARBURETOR.......................................................................................23
PARTS – COOLANT SYSTEM ...............................................................................24
PARTS – ELECTRICAL SYSTEM............................................................................25
PARTS – ENGINE – BOTTOM END AND TRANSMISSION..........................................26
Parts – Engine Clutch and Kicker................................................................27
Parts – Engine – Water Pump .....................................................................28
Parts – Engine – Top End............................................................................29
PARTS – EXHAUST SYSTEM................................................................................30
PARTS – FORKS & TRIPLE CLAMPS.....................................................................31
PARTS – FORKS – LEG ASSEMBLY......................................................................32
PARTS – FRAME I ..............................................................................................33
Parts – Frame II...........................................................................................34

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PARTS – FRONT BRAKES....................................................................................35
PARTS – FRONT WHEEL.....................................................................................36
PARTS – PLASTIC BODYWORK & SEAT................................................................37
PARTS – REAR BRAKE .......................................................................................38
PARTS – REAR WHEEL.......................................................................................39
PARTS – SHOCK................................................................................................40
PARTS –SWINGARM ASSEMBLY..........................................................................41
SERVICE............................................................................................................42
ENGINE SERVICE ...............................................................................................42
Base Gasket Selection ................................................................................43
Engine Removal ..........................................................................................45
Complete Engine Disassembly Procedure ..................................................45
Top End Disassembly Procedure ................................................................46
Splitting the Cases.......................................................................................47
Engine assembly .........................................................................................47
CLUTCH ............................................................................................................49
IGNITION ...........................................................................................................55
COOLING SYSTEM..............................................................................................57
FUEL &AIR SYSTEM ..........................................................................................60
EXHAUST ..........................................................................................................63
BRAKES ............................................................................................................64
FRONT FORKS...................................................................................................64
REAR SHOCK ....................................................................................................66
TUNING..............................................................................................................67
CLUTCH ............................................................................................................67
GEARING...........................................................................................................69
SUSPENSION.....................................................................................................71
CARBURETION ...................................................................................................72
TROUBLESHOOTING........................................................................................75
INDEX.................................................................................................................76

5
General Information
Specifications - General
Items CX50 SR
Dimensions
Wheelbase 39” (991mm)
Wheel size 10” (254mm) rear, 12” (305mm) front
Seat height 26” (660mm)
Engine
Type 2-stroke, single cylinder, reed valve
Cooling system Liquid-cooled
Coolant 50/50 antifreeze-coolant / distilled water
Displacement 49.8 cc
Bore and stroke 39 mm x 41.7 mm
Ignition system PVL Analogic
Spark plug Champion 8339-1, 8332-1 hotter, 8904-1 colder
Gap 0.023” – 0.025” (0.58 – 0.64 mm)
Ignition timing 0.035” (0.9 mm) Before Top Dead Center (BTDC)
Fuel type High octane pump gasoline
RACE FUELS ARE NOT RECOMMENDED
Premix Oil type Motul 800 2T
Premix oil ratio after break-in Motul 800 2T Off Road, 50:1 to 63:1
All other premix oil at 32:1 to 40:1
Carburetion 19 mm Dell’Orto
Slow (Pilot) Jet / Main Jet 60 / 96
Float Height 16mm + 0.5mm (0.63” + 0.020”)
Transmission
Speed Single
Final drive ratio 14/38 T
Chain 100 links 420
Transmission / clutch oil type Cobra Venom 3 Shoe Clutch Milk
Quantity 235 – 350 ml (8 – 12oz)

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Chassis
Front tire 2.50 - 12
Pressure 16 psi minimum
Rear tire 2.75 - 10
Pressure 16 psi min. (20 psi for hard pack or rocky conditions)
Front fork Cobra 30mm USD
Fork oil type SAE 5 weight
Fork oil amount 107 ml (3.6oz)
Rear shock (std. settings) Compression 16 clicks out
Rebound 12 clicks out
Optional Components
Call your dealer, or the factory, for details
• Carburetor jets / reeds
• Flat clutch washers (see clutch service section)
• Pre filter for the airbox
• Sprockets
o Front
o Rear
• Suspension Springs
Weight of Rider (lb) Fork Spring Shock Spring
Less than 51 0.23 kg/mm
KCKG1223
gray, 3.5 kg/mm
SCKGFX35
51 - 60 0.25 kg/mm
KCKG1206
yellow, 3.7 kg/mm
SCKGFX37
Greater than 60 0.27 kg/mm
KCKG1227
gold, 3.9 kg/mm
SCKGFX39
• Tires, tubes or ‘Tire Balls’
Specifications - Torque Values
Torque Value
Fastener ft-lb in-lb Nm Size & Remarks
Cylinder head
nuts 8.8 105 12 M6 x 1.0

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Crankcase
bolts 8.8 105 12 M6 x 1.0
Spark plug (SP) (SP) (SP) M14 x 1.25
Stator bolts 2.1 25 2.8 M5 X 0.8
Stator cover
bolts 1.7 20 2.3 M4 X 0.75
Clutch cover
bolts 5.8 70 7.9 M6 X 1.0
Clutch nut 40 480 54 M10 x 1.25*
Clutch bolts 12 144 16 M6 x 1.0
CFD nut 55 664 75 ½” x 20 LHT
Front axle nut 25 300 34 M12 x 1.25
Engine mount
bolts 22 265 30 M8 X 1.25
Swingarm
Pivot 21 250 28 M14 X 2.0
Shock Bolt 35 420 47 M10 x 1.5**
Water Pump
Impeller 6 75 8 M5 x 0.8**
Water Pump
Pulley 10 124 14 M6 x 1.0**
Intake manifold
bolts 4.6 55 6.2 M6 X 1.0
Rear Axle Bolt 25 300 34 M12 X 1.25
Rear Sprocket
Bolts 18 216 24 7 mm**
Fork cartridge
rod 12 144 16
Triple clamp
bolts (bottom) 6 72 8 M6 x 1.0
Triple clamp
bolts (top) 9 108 12 M6 x 1.0
Fork cap 5 60 6.7 1.25” x 18
Ignition rotor
nut 35 420 47 M10 x 1.25*
* Apply high strength thread locking agent when installing
** Apply medium strength thread locking agent when installing
(SP) To apply the proper torque to the spark plug when inserting, one must first
screw the spark plug in until the metal gasket ring causes resistance and then
turn another 1/8 to ¼ turn.

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Break-In Procedure
Your Cobra CX50 JR is a close-tolerance high performance machine and break-
in time is very important for maximum life and performance. The CX50 JR can be
ridden hard after the first ½ hour break-in time.
Cobra recommends Motul 800 T2 premix oil with high octane
pump gas mixed at 50:1 (50 ml oil to 1.3 gallon of gas, or 38ml oil to 1 gallon of
gas). Other brands of oil should be mixed at 32:1 for break-in.
CAUTION:
Failure to use proper fuel, oil, or fuel/oil mixture may result in premature engine
wear or damage to the machine.
Adhering to the following break-in schedule will result in long lasting high
performance machine.
• Start bike on stand
• First 5 minute period, operate the bike on the stand with a combination of idle
and high RPM operation. (avoid prolonged high RPM but spin the rear
wheel good at least once or twice per minute)
• Allow bike to cool
• Ride for 15 minutes maximum (avoid prolonged high RPM operation and
avoid abusing the clutch with throttle blipping.
• Cool and inspect bike for loose fasteners.
• Next ½ hour of operation, avoid prolonged operation at Wide Open Throttle.
• After 1 hour of operation
o Check for loose bolts and nuts on the bike and retighten as
necessary (proper toque values are listed under Specifications).
o Clean the carburetor bowl.
o Change the transmission / clutch lubricant.
• After 8 hours of operation
o Change the fork oil.
o Have a Certified Cobra Mechanic change the shock oil.
• Your bike is now ready for the highest level of competition!
NOTE:
During break-in the bike will likely lose some engine coolant through the radiator
overflow hose. Losing up to 4 oz (120 ml, ½ cup) is normal. Proper coolant level
will cover the top of the radiator cores. Removing the radiator cap and looking
inside is the only way to check the coolant level.

9
Never open the radiator cap of a machine that has a hot or warm engine or one
that has recently been ridden. Burning and scalding could occur.
CAUTION:
It is important that the radiator cap is installed correctly and completely otherwise
engine damage could occur.
Starting Procedure
Before starting the machine inspect the following:
• Check for proper tire pressure in both tires.
• Observe the chain tension and adjust if necessary.
• Observe the coolant level and fill if necessary.
• Verify that the chain rollers and sliders do not have improper wear.
• Verify that the handlebars are tight.
• Check the throttle for smooth operation and that it ‘clacks’ shut properly.
• Check for loose bolts and nuts, and re-torque as necessary.
• Verify that the air filter is clean and properly saturated with oil.
• Insure that the fuel tank contains an adequate volume of fuel / oil mixture to
complete the distance required. (High octane pump gas with Motul 800 2T
premix oil)
• Turn the fuel on by rotating the fuel petcock knob to the vertically downward
position (reserve position is horizontally forward)
CAUTION:
For best results from your Cobra Motorcycle use only the recommended fuels.
Testing has shown that most ‘race’ fuels actually degrade performance.
Always wear a helmet and other protective riding gear.
When your pre-ride inspection is complete the bike may be started. For a cold
engine follow this procedure.
1. Place the motorcycle on a stand of sufficient strength that positions the
motorcycle in a level upright position with the rear wheel off the ground.
2. Pull up the choke knob and turn it to lock it.
3. Kick start the engine.
4. Rev the engine in short spurts, turning the throttle no more than 1/4 open
until the engine will run without the choke.
5. Verify a functional engine shut-off switch by shutting off the engine.
6. Restart the engine and proceed with riding when the engine is sufficiently
warm (i.e. the side of the cylinder is warm to touch).