Cobra CX50P3 User manual

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 CX50P3 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.
MCCL2017.0

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..........................................................................................12
Air Filter Cleaning........................................................................................................13
Fork Maintenance .......................................................................................................14
Fork Air Bleeding.....................................................................................................15
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 ........................................................24
Parts – Engine Clutch and Kick Lever.........................................................................26
Parts – Engine – Water Pump.....................................................................................28
Parts – Engine – Top End...........................................................................................29
Parts – Exhaust System..............................................................................................30
Parts – Forks & Triple Clamps....................................................................................32
Parts – Forks – Leg Assembly....................................................................................34
Parts – Frame – Mounting Hardware I........................................................................36
Parts – Frame – Mounting Hardware II.......................................................................37
Parts – Front Brakes...................................................................................................38
Parts – Front Wheel....................................................................................................39
Parts – Plastic & Seat .................................................................................................40

3
Parts – Rear Brake......................................................................................................41
Parts – Rear Wheel.....................................................................................................42
Parts – Shock..............................................................................................................43
Parts – Shock - Internal...............................................................................................44
Parts – Swingarm Assembly.......................................................................................45
Service............................................................................................................................46
Engine Service............................................................................................................46
Base Gasket Selection............................................................................................47
CFD Adjustment......................................................................................................48
Engine Removal......................................................................................................49
Complete Engine Disassembly Procedure..............................................................50
Top End Disassembly Procedure............................................................................50
Splitting the Cases..................................................................................................51
Engine assembly.....................................................................................................52
Clutch..........................................................................................................................53
Clutch Assembly .....................................................................................................57
Ignition.........................................................................................................................58
Cooling System...........................................................................................................59
Fuel & Air System .......................................................................................................61
Carburetor...............................................................................................................61
Reeds......................................................................................................................63
Exhaust.......................................................................................................................63
Rear wheel pullers ..................................................................................................63
Brakes.........................................................................................................................64
Rear Shock .................................................................................................................66
Tuning.............................................................................................................................67
Suspension .................................................................................................................71
Adjustment ..............................................................................................................71
Front Fork Operation...............................................................................................72
Carburetion .................................................................................................................72
Troubleshooting..............................................................................................................75

4
General Information
Specifications - General
Items CX50 P3
Dimensions
Wheelbase 35.75” (908mm)
Wheel size 10” (254mm)
Seat height 22” (558 mm)
Engine
Type 2-stroke, single cylinder, reed valve
Cooling system Liquid-cooled
Coolant Moto Chill
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 12 mm Dell’Orto
Slow (Pilot) Jet / Main Jet 55 / 92
Needle - position W7-2
Slide #50
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 300 ml (10oz)
Chassis
Front tire 2.75 (80/100) – 10"
Pressure 15 psi minimum
Rear tire 2.75 (80/100) – 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: 3 out,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)
y
ellow
46 to 55 (stiff) KCCJ3225
(
25 lb/in
,
4.40 N/mm
)
SCMUOH06 (295 lb/in)
white
Specifications - Torque Values
Fastener Torque Value
Loctite TM Size & Remarks
ft-lb in-lb Nm
Cylinder head nuts 9 110 12 M6 X 1.0
Cylinder nuts 22 265 3.0 M8 x 1.25**
Crankcase bolts 8.8 105 12 M6 x 1.0
Spark plug (SP) (SP) (SP) M14 x 1.25
Stator bolts 2.1 25 2.8 243 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 54 263 10 x 1.25
Clutch bolts 12 144 16 263 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 47 243 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 5 243 M5 x 0.8
Intake manifold bolts 4.6 55 6.2 M6 X 1.0
Ignition rotor nut 33 400 45 243 M10 x 1.25
Rear brake rotor bolts 9 108 12 243 M6 x 1.0
Rear sprocket bolts 16 195 22 243 M7 X 1.0
Axle nuts 25 300 34 M12 X 1.25
** Use a ‘crows foot’ attachment oriented 90° to the torque wrench
(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 P3 is a close-tolerance high performance machine and break-
in time is very important for maximum life and performance. The CX50 P3 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 three digits indicate the model while the sixth and seventh
indicates the model year.
a. Example, CP3xx17xxx is a 2017 CX50 P3.
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

9
cases and can damage the stator as it cools off because of lack of airflow
around the stator.
8. If you ever need to weld anything on the bike, disconnect the spark plug
cap, unplug the ignition, disconnect the kill switch, scrape the paint bare
near the area to be welded and put the ground clamp as close to the area
to be welded as possible.
Be sure the fuel tank and carburetor have been removed and safely located
away from the welding process.
9. The frame is 4130 Chrome Moly and it is important to weld it with the proper
rod and heat settings set as light as possible. Cobra recommends replacing
the frame with a new one if the old one becomes damaged. Use ER70S6
filler if welding on the frame.
10. If your kick-starter lever does not return properly, first try loosening the six
kick/clutch cover screws ½ turn. Hold the kick lever ½ way down while
retightening the six screws starting for the center and working out
11. Inspect CFD slip torque after the 2
nd
ride and then again after the 6
th
ride.
After this follow the recommended schedule below.
12. Check proper clutch engagement before and after each ride. If the clutch is
engaging properly DO NOT feel the need to take the clutch apart to;
measure the spring stack, clean the stack, replace the springs, etc... Cobra
has worked very hard to make a clutch that is low maintenance and so only
take it apart if it NEEDS to be maintained.
Schedule
Prior to each ride
oCheck that the air filter is cleaned and oiled.
oInsure the smooth operation of the throttle cable (throttle soundly ‘clacks’
shut).
oCheck for frayed strands of the throttle cable inside the throttle housing.
oCheck for adequate tire pressure.
oCheck all nuts and bolts for proper torque.
oSpray all moving parts with WD40 or other light oil.
oCheck drive chain for
Proper tension.
Adequate lubrication.
oInsure that the ignition stator and rotor are clean and dry.
oCheck the frame for cracks in the metal or cracks in the paint that might
Indicate that the metal has been stressed beyond its safe limits.
oCheck the rims for signs of stress, like cracks around the rim, spokes
and hub.
oEqualize the pressure in the forks with atmosphere.
Every 2 hours of operation
oReplace the transmission oil.
oCheck the CFD torque

10
Every 10 hours of operation
oReplace the fork oil.
oHave the shock oil replaced by a Certified Cobra Mechanic.
Replacing Transmission / Clutch Lubricant
Tools needed:
5mm allen wrench
Minimum of 300 ml (10 oz) Cobra Venom 3 Shoe Clutch Milk (Part
#MCMUGF32).
Procedure:
1. Begin this procedure with a bike that has been ridden more than 5 minutes
but less than 10 minutes. It is desired to have the engine warm enough so
that the oil is ‘runny’ but not so hot that there is risk of being burned by the
engine or the oil.
Hot oil and hot components on the motorcycle may cause burns.
2. Remove the oil drain plug located on the right side of the engine, on the
clutch cover, near the brake lever (figure 1).
3. After it has drained, reinstall the plug, being sure that the gasket is in place.
4. Reapply oil from oil fill plug 300 cc (10 oz) Cobra Venom 3 Shoe Clutch Milk
thru the oil fill plug.
NOTE: Putting additional oil, up to 350 ml (12 oz), can help clutch life. More than
350 ml (12 oz) will degrade engine performance.
NOTE: It can be helpful to lean the bike over on its left side to add oil to the bike.
5. Reapply the oil fill plug, hand tight, being sure the gasket is in place.
Figure 1