Cobra Moto CX50 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 Moto, LLC
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 CX50JR 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.
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.
MCCJ2014.0

2
Table of Contents
General Information..............................................................................................4
Specifications - General....................................................................................4
Optional Suspension Components....................................................................5
Specifications - Torque Values..........................................................................5
Break-In Procedure...........................................................................................6
Starting Procedure ............................................................................................7
Maintenance .........................................................................................................8
Tips ...................................................................................................................8
Schedule...........................................................................................................9
Replacing Transmission / Clutch Lubricant.....................................................10
Proper Chain adjustment.................................................................................11
Rear Brake Maintenance.................................................................................11
Brake Bleeding Procedure ..............................................................................13
Air Filter Cleaning............................................................................................14
Fork Oil Replacement......................................................................................15
Cobra Frictional Drive (V3 CFD) .....................................................................16
Parts ...................................................................................................................18
Parts –Airbox and Inlet System......................................................................18
Parts –Bars and Controls...............................................................................19
Parts - Carburetor............................................................................................20
Parts –Coolant System...................................................................................21
Parts –Electrical System ................................................................................22
Parts –Engine –Bottom End and Transmission.............................................23
Parts –Engine Clutch and Kicker....................................................................24
Parts –Engine –Top End...............................................................................26
Parts –Exhaust System..................................................................................27
Parts –Forks & Triple Clamps ........................................................................28
Parts –Forks –Leg Assembly –Brake Side...................................................29
Parts –Forks –Leg Assembly –Non-Brake Side ...........................................30
Parts –Frame –Mounting Hardware I ............................................................31
Parts –Frame –Mounting Hardware II ...........................................................32
Parts –Front Brakes .......................................................................................33
Parts –Front Wheel ........................................................................................34

3
Parts –Plastic & Seat......................................................................................35
Parts –Rear Brake..........................................................................................36
Parts –Rear Wheel.........................................................................................37
Parts –Shock..................................................................................................38
Parts –Shock - Inside.....................................................................................39
Parts –Swingarm Assembly ...........................................................................40
Service................................................................................................................41
Engine Service................................................................................................41
Base Gasket Selection ................................................................................42
Engine Removal ..........................................................................................44
Complete Engine Disassembly Procedure ..................................................44
Top End Disassembly Procedure ................................................................45
Splitting the Cases.......................................................................................46
Engine Assembly.........................................................................................46
Clutch..............................................................................................................48
Ignition.............................................................................................................52
Cooling System...............................................................................................54
Radiator fluid removal:.................................................................................54
Fuel & Air System............................................................................................57
Carburetor....................................................................................................57
Reeds..........................................................................................................59
Exhaust...........................................................................................................59
Wheels & Tires................................................................................................59
Rear wheel pullers.......................................................................................60
Brakes.............................................................................................................60
Rear Shock .....................................................................................................62
Tuning.................................................................................................................63
Gearing ...........................................................................................................66
Suspension .....................................................................................................67
Rear shock...................................................................................................68
Front Forks ..................................................................................................69
Carburetion .....................................................................................................69
Troubleshooting..................................................................................................73
Index...................................................................................................................75

4
General Information
Specifications - General
Items
CX50 JR
Dimensions
Wheelbase
35.75” (908mm)
Wheel size
10” (254mm)
Seat height
23.9” (607 mm)
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
Electronic, analogic advance
Spark plug
Autolite - XS61 & 4261
Gap
0.023” – 0.025” (0.58 – 0.64 mm)
Ignition timing
0.040” (1.0 mm) Before Top Dead Center (BTDC)
Fuel type
High octane pump gasoline
Premix Oil type
Bel-Ray H1-R
Premix oil ratio after break-in
40:1 to 50:1
Carburetion
14 mm Dell’Orto
Slow (Pilot) Jet / Main Jet
55 / 92
Float Height
16mm + 0.5mm (0.63” + 0.020”)
Transmission
Speed / Clutch
Single / Cobra 3 shoe
Final drive ratio
14/37 T
Chain
420
Transmission / clutch oil type
Cobra Venom 3 Shoe Clutch Milk
Quantity
235 –350 ml (8 –12oz)
Chassis
Front tire
2.50 –10
Pressure
15 psi minimum
Rear tire
2.75 –10
Pressure
15 psi min. (20 psi for hard pack or rocky conditions)
Front fork
CARD 32mm USD Fully Adjustable w/ Smart Leg
Fork oil type
2.5wt Bel-Ray Fork Oil
Fork oil amount
145 ml
Std settings
Rear Shock ( std settings)
Smart leg: 3out,Compression and rebound 1 1/2 out
Compression Low 7, High 7, No Rebound Adj.

5
Optional Suspension Components
Weight of Rider (lb)
Fork Spring
Shock Spring
Less than 38 (light)
KCCJ3218
(18 lb/in, 3.15 N/mm)
SCMUOH04 (275 lb/in) red
38 –45 (std)
KCCJ3221
(21 lb/in, 3.70 N/mm)
SCMUOH05 (285 lb/in)
yellow
46 to 55 (stiff)
KCCJ3225
(25 lb/in, 4.40 N/mm)
SCMUOH06 (295 lb/in)
white
Specifications - Torque Values
Fastener
Torque Value
Size & Remarks
ft-lb
in-lb
Nm
Cylinder head nuts
10.3
123
14
M7 X 1.0
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
10 x 1.25*
Clutch bolts
12
144
16
M6 x 1.0*
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**
Triple clamp (top)
12
144
16
M8 x 1.25
Triple clamp (bottom)
6
72
8
M6 x 1.0
Water pump impeller
3.6
44
5
M5 x 0.8*
Intake manifold bolts
4.6
55
6.2
M6 X 1.0
Ignition rotor nut
33
400
45
M10 x 1.25**
Rear sprocket bolts
18
216
24
M7 X 1.0**
Axle nuts
25
300
34
M12 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, first screw the
spark plug in until the metal gasket ring causes resistance and then turn another
¼ turn.

6
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 Bel-Ray H1-R premix oil with high octane
pump gas mixed at 40:1 (150 ml oil to 2 gallons 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.
Allow bike to cool and inspect bike for loose fasteners.
Avoid prolonged operation at Wide Open Throttle for the next half hour.
After 1 hour of operation
oCheck for loose bolts and nuts.
oClean the carburetor bowl.
oChange the transmission / clutch lubricant.
Check CFD torque and adjust as necessary
After 8 hours of operation
oChange the fork oil.
oHave a Certified Cobra Mechanic or suspension specialist 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) 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.
Never remove the radiator cap of a machine that has a warm engine. Burning
and scalding could occur.

7
Starting Procedure
Before starting the machine inspect the following:
Tire pressure
Chain tension
Coolant level
Proper wear on chain rollers and sliders
Handlebar tightness
Throttle assembly movement/cable adjustment
Air Filter
Check for loose nuts and bolts
Turn the fuel on by rotating the fuel petcock knob to the vertically downward
position (reserve position is horizontally forward)
NOTE: For best results from your Cobra Motorcycle use only the recommended
fuel. 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).
CAUTION:
Never rev an engine full throttle until the engine is at operating temperature.
This is a high performance race motorcycle. Too much application of throttle will
likely land your little racer on his or her arse. Fenders can be replaced but
bruised egos and other body parts take longer.
CAUTION:
Cobra recommends that you tell your child to take it easy the first couple of
minutes in practice until the engine comes up to full operating temperature.
CAUTION:
Make sure your riders’ foot is not resting on the foot brake while they are riding.

8
Maintenance
A properly maintained machine is safer, faster, and more fun to ride. It is
important that you adhere to this maintenance schedule so as to promote the
longevity of your Cobra Motorcycle
Tips
1. Recommended lubricants:
a. Cobra Clutch Milk is by far the best auto clutch lubricant. It is a
full synthetic lubricant that has been specifically formulated for
Cobra’s auto clutch and has;
Exceptional film strength over petroleum based oils or
synthetic blends.
Extreme temperature tolerance.
NO frictional modifiers.
Dispersant package to keep clutch fibers in suspension so
they can be flushed out when the oil is changed.
Extremely low viscosity for minimal drag and ‘windage’.
b. Bel-Ray H1-R oil is the recommended premix oil because:
Its Ester base leaves a film on all parts at all times. No metal
to metal startups or corrosion potential.
Exception film strength over petroleum based oils or other
synthetic blends.
Easily atomizes and burns completely.
Does not fall out of suspension from premix in cold weather.
Produces virtually no coking deposits, leaving pistons, rings
and heads extremely clean with minimal pipe ‘spooge’.
2. Filling your transmission with more than 8.0 oz (235 cc) of lubricant will help
to transfer heat from the clutch. Filling with more than 12 oz (295 cc) will
degrade performance.
3. The cylinder base gasket has been ‘fitted’ for your engine. The code
number stamped into the engine cases will guide you to what thickness
base gasket is required during a common top end service. See the service
section of this manual to correspond a code number with a base gasket part
number.
4. Evaluate the bikes jetting only after it has been warmed up to race
temperatures.
5. New chains will stretch on first use. Never install a new chain prior to a
race. Always ‘break’ them in during practice.
6. Your Cobra motorcycle has a 10 digit VIN (Vehicle Identification Number).
The first two digits indicate the model and the seventh indicates the model
year (MY). Example, CMxxxx7xxx is a 2007 MY CX50 JR.
7. Because of the amount of heat generated by the clutch and engine during
extended periods of riding, it is advisable to remove the ignition cover
afterward to allow the ignition to cool off. The heat transfers through the
cases and can damage the stator as it cools off because of lack of airflow
around the stator.