Cobra CX50-OI 2007 User manual

Owners
Parts
Service
Tuning
2007 CX50-OI

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 Road
Hillsdale, MI 49242
1

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 CX50 OI 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 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.
MCP32007.4
2

Table Of Contents
General Information..............................................................................................5
Specifications - General....................................................................................5
Specifications - Torque Values..........................................................................6
Optional Components........................................................................................7
Break-In Procedure...........................................................................................8
Starting Procedure ............................................................................................9
General Tips....................................................................................................10
Maintenance .......................................................................................................10
Schedule & Tips..............................................................................................10
Replacing Transmission / Clutch Lubricant .....................................................11
Chain adjustment ............................................................................................13
Front brake adjustment ...................................................................................13
Rear brake adjustment....................................................................................14
Air Filter Cleaning............................................................................................15
Fork Oil Replacement......................................................................................16
Exhaust Power Regulator................................................................................17
Parts ...................................................................................................................18
Parts – Airbox and Inlet System I....................................................................18
Parts – Bars and Controls ...............................................................................20
Parts – Carburetor...........................................................................................21
Parts – Coolant System...................................................................................22
Parts – Electrical System ................................................................................23
Parts – Engine – Bottom End & Transmission ................................................24
Parts – Exhaust System..................................................................................29
3

Parts – Forks and Triple Clamps.....................................................................30
Parts – Frame – Mounting Hardware I ............................................................32
Parts – Front Brakes .......................................................................................35
Parts – Front Wheel ........................................................................................36
Parts – Oil Reservoir.......................................................................................37
Parts – Plastic Bodywork & Seat.....................................................................38
Parts – Rear Brake..........................................................................................39
Parts – Rear Wheel.........................................................................................40
Parts – Shock..................................................................................................41
Parts – Swingarm Assembly............................................................................42
Service................................................................................................................43
Engine.............................................................................................................43
Clutch..............................................................................................................43
Reeds..............................................................................................................44
Carburetor.......................................................................................................46
Exhaust ...........................................................................................................49
Rear wheel pullers...........................................................................................49
Tuning.................................................................................................................50
Suspension .....................................................................................................50
Gearing ...........................................................................................................53
Carburetion .....................................................................................................54
Troubleshooting..................................................................................................57
4

General Information
Specifications - General
Items CX50 OI
Dimensions
Wheelbase 35.75” (908mm)
Wheel size 10” (254mm)
Seat height 22” (559 mm)
Engine
Type 2-stroke, single cylinder, reed valve
Cooling system Liquid-cooled
Displacement 49.8 cc
Bore and stroke 39 mm x 41.7 mm
Ignition system Digital Electronic
Spark plug Champion 8339-1, 8332-1 hotter, 8904-1 colder
Gap 0.023” – 0.025” (0.58 – 0.64 mm)
Fuel type high octane pump gasoline
RACE FUELS ARE NOT RECOMMENDED
Injector oil type Cobra Venom 2-cycle Race Oil
Fuel / oil mix ratios Fill oil reservoir as required
Ignition timing Fixed
Carburetion 12 mm Dell’Orto PHVA – PS
Main jet 82
Slow (Pilot) jet 42
Float height Non adjustable
Coolant 50/50 antifreeze-coolant / distilled water
Transmission
Speed Single
Clutch 3 shoe centrifugal
Final drive ratio 10/44 T
Transmission / clutch oil type Cobra Venom 3 Shoe Clutch Milk
Quantity 250 ml (8.5oz)
5

Chassis
Front tire 2.50 – 10
Pressure 20 psi minimum
Rear tire 2.50 – 10
Pressure 20 psi minimum
Front fork Marzocchi 32mm
Fork oil type SAE 20 weight
Fork oil amount 200 ml (6.8 oz) oil change, 220 ml (7.4 oz) rebuild
Fork oil height 70 mm (2.75”) collapsed from top with spring (no
spacer)
Specifications - Torque Values
Torque ValueFastener
ft-lb in-lb Nm
Size &
Remarks
Cylinder head nuts 8.8 105 12 M6 X 1.0
Front engine mount bolts 22 264 30 M8 x 1.25
Rear engine mount bolts 22 264 30 M8 x 1.25
Swingarm pivot bolt 21 250 28 M14 x 2
Rear sprocket bolts 18 216 24 M7 x 1
Rear axle bolts 25 300 34 M12 x 1.25
Rear shock mounts 40 480 54 M10 x 1.5
Clutch adjust access plug 10 120 14 M12 x 1.25
Clutch nut 30 360 42
Flywheel nut 30 360 42
Units of mm unless otherwise specified
6

Optional Components
Call your dealer, or the factory, for details
• Carburetor jets
o Main jets #’s 74, 76, 78, 80, 84, 86, 88, 90, 92, 94
o Slow jets #’s 38, 40, 42, 45,
• Exhaust Power Regulator, ECPW0001
• Pre-filter for Airbox
• Sprockets
o Front sprocket, 11T
o Rear sprocket, 39 T – 45 T
• Suspension Springs
Weight of Rider (lb) Fork Spring Shock Spring
Less than 38 (light) KCMZ0012A
(12 lb/in, 2.10 N/mm)
SCMUOH04
(red) 275 lb/in
38 – 45 (std) KCMZ0012
(14 lb/in, 2.45 N/mm)
SCMUOH05
(yellow) 285 lb/in
46 to 55 (stiff) KCMZ0012B
(16 lb/in, 2.80 N/mm)
SCMUOH06
(white) 295 lb/in
• Tires
• Tubes or ‘Tire Balls’
7

Break-In Procedure
Your Cobra CX50 OI is a close-tolerance high performance machine and break-
in time is very important for maximum life and performance. The CX50 OI can be
ridden hard after the first ½ hour break-in time but it is recommended that no
adjustments are made to the suspension until the full 8 hours of bike break-in has
elapsed. Also, after the engine, transmission, and drive train have been broken-in
for the full 8 hours, the bike will be faster!
Fill the fuel tank with high octane pump gas (premix is acceptable not
necessary). Also, fill the oil injection reservoir with Cobra’s specially formulated
Cobra Venom 2-cycle Race Oil. (Part # MCMUOL02)
CAUTION:
Failure to use proper fuel or oil 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!
8

Starting Procedure
Before starting the machine inspect the following:
• Make sure vehicle is properly maintained (see Schedule & Tips in the
Maintenance section)
• Fill the 2-stroke injector oil reservoir with Cobra’s specially formulated Cobra
Venom 2-cycle Race Oil.
• Insure that the fuel tank contains an adequate volume of fuel to complete
the distance required. (high octane pump gas).
• Check the throttle for smooth operation and sound closing.
• 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.
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. On the carburetor, flip the black choke knob upward from the right side of
the bike.
3. Kick start the engine by kicking the lever forward.
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 when it's cold or slightly warmed up. Also, for
best clutch performance, warm up the bike before taking off.
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.
9