Cobra 2004 cm50 User manual

2004 CM50
Owners / Service / Parts
“CHAMPIONS START HERE”

1
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.
11511 Springfield Road
North Lima, Ohio 44452 MCCM2004.2

2
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 CM50 IS A COMPETITION MODEL ONLY AND IS NOT
MANUFACTURED FOR, NOR SHOULD IT BE USEDON 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.

3
Table Of Contents
Specifications -General..................................................................................................5
Specifications -Torque Values ......................................................................................7
Optional Components......................................................................................................8
Break-In Procedure..........................................................................................................9
Starting Procedure.........................................................................................................10
General Tips....................................................................................................................11
Maintenance....................................................................................................................12
Schedule & Tips .........................................................................................................12
M1: Replacing Transmission / Clutch Lubricant....................................................13
M2: Chain adjustment................................................................................................14
M3: Front brake adjustment......................................................................................15
M4: Rear brake adjustment ......................................................................................15
M5: Air Filter Cleaning ...............................................................................................16
M6: Fork Oil Replacement........................................................................................17
Parts.................................................................................................................................18
Parts –Airbox and Inlet System...............................................................................18
Parts -Carburetor.......................................................................................................20
Parts –Coolant System.............................................................................................21
Parts –Electrical System..........................................................................................22
Parts –Engine –Bottom End and Transmission..................................................23
Parts –Engine –Clutch and Kick Starter...........................................................24
Parts –Engine –Ignition and Water Pump........................................................25
Parts –Engine –Top End.....................................................................................26
Parts –Exhaust System............................................................................................27
Parts –Forks & Triple Clamps.................................................................................28
Parts –Forks –Leg Assembly.............................................................................29
Parts –Frame –Engine, Tank, and Pipe Mounts, Brake Snake........................30
Parts –Frame –Seat, Fender, R Side Panel, Brake Pedal, Silencer & Shock
Mounts......................................................................................................................31
Parts -Frame –Radiator, Footpeg, Chain Roller, and Airbox Mounts..........32
Parts –Front Brakes..................................................................................................33

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Parts –Front Wheel...................................................................................................34
Parts –Plastic Bodywork & Seat.............................................................................35
Parts –Rear Brake.....................................................................................................36
Parts –Rear Wheel....................................................................................................37
Parts –Shock..............................................................................................................38
Parts –Swingarm Assembly.....................................................................................39
Service.............................................................................................................................40
Engine Service............................................................................................................40
Engine Removal.....................................................................................................41
Complete Engine Disassembly Procedure.........................................................42
Top End Disassembly Procedure........................................................................42
Splitting the Cases.................................................................................................43
Engine assembly....................................................................................................44
Clutch...........................................................................................................................49
Ignition..........................................................................................................................53
Cooling System...........................................................................................................55
ES6: Fuel & Air System.............................................................................................59
Exhaust........................................................................................................................62
Wheels & Tires ...........................................................................................................63
CS2: Suspension........................................................................................................65
Troubleshooting..............................................................................................................66
Index.................................................................................................................................67

5
Specifications -General
Items CM 50
Dimensions
Wheelbase 35.75” (908mm)
Wheel size 10” (254mm)
Seat height 23.9” (607 mm) Stock #TCHJ0001
22” (559 mm) Optional # TCHO0001
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 Electronic
Spark plug Champion 8339-1, 8332-1 hotter, 8904-1 colder
Gap 0.023” –0.025” (0.58 –0.64 mm)
Ignition timing 0.050” (1.3 mm) Before To Dead Center (BTDC)
Fuel type High octane pump gasoline
RACE FUELS ARE NOT RECOMMENDED
Oil type Cobra Venom 2-cycle Race Oil
Fuel / oil mix ratios Between 32:1 and 40:1 (after engine Break-In)
Carburetion 14 mm Dell’Orto
Main Jet 92
Slow (Pilot) jet 55
Float Height 16mm +0.5mm (0.63” +0.020”)
Transmission
Speed Single
Clutch Cobra 3 shoe
Final drive ratio 13/37 T
Chain 88 links 420
Transmission / clutch oil type Cobra Venom 3 Shoe Clutch Milk, or Dexron III
Quantity 235 ml (8.0oz)

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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 Marzocchi 32mm
Fork oil type SAE 20 weight
Fork oil amount 200 ml (6.8 oz) oil change, 220 ml (7.4 oz) rebuild
Collapsed fork oil height 70 mm (2.75”) spring in, no spacer

7
Specifications -Torque Values
Torque Value
Fastener ft-lb in-lb Nm Size & Remarks
Cylinder head nuts 9.2 110 12 ¼”
Crankcase bolts 6.6 80 96 x 1.0
Spark plug (SP) (SP) (SP) 14 x 1.25
Stator bolts 2.1 25 2.8 #8
Stator cover bolts 1.7 20 2.3 #8
Clutch cover bolts 5.8 70 7.9 6 mm
Clutch 40 480 54 10 x1.25***
Engine mount bolts 22 265 30 8 mm
Swingarm Pivot 21 250 28 14 mm
Intake manifold bolts 4.6 55 6.2 6 mm
Ignition rotor nut 40 480 54 10 x 1.25 mm**
Rear Sprocket Bolts 18 216 24 7 mm
Rear shock mounts 40 480 54 10 x 1.5
Rear Axle Bolt 25 300 34 12 mm
** Use green (wicking / bearing retainer) thread locker, with primer, on the
flywheel / crankshaft taper but none on the threads.
*** Use green (wicking / bearing retainer) thread locker, with primer, on the
crankshaft / clutch taper but use red (high strength) thread locker, with primer, on
the nut.
(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.

8
Optional Components
Call your dealer, or the factory, for details
•Carburetor jets
•Sprockets
oFront
oRear
•Suspension Springs
Weight of Rider (lb) Fork Spring Shock Spring
Less than 38 (light) KCMZ0012A SCMUOH04 (275 lb/in)
38 –45 (std) KCMZ0012 SCMUOH05 (285 lb/in)
46 to 55 (stiff) KCMZ0012B SCMU0H06 (295 lb/in)
•Suspension Valving
Damping Rate Fork Valving
Compression
(right)
Fork Valving
Rebound
(left)
Shock Valving
(kit)
Soft (fast) KCMZ0033A KCMZ0032A SCMUOH07
Standard KCMZ0033KCMZ0032 SCMUOH08
Hard (slow) KCMZ0033B KCMZ0032B SCMUOH09

9
Break-In Procedure
Your Cobra CM50 is a close-tolerance high performance machine and break-in
time is very important for maximum life and performance. The CM50 can be
ridden hard after the first ½ hour break-in time but it is recommended that no
adjustments are made to the carburetion or 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!
Use a fuel / oil mixture of 32:1 for the full 8 hour break-in period. Be sure to use
high octane pump gas with Cobra’s specially formulated Cobra Venom 2-cycle
Race Oil. (Part # MCMUOL02)
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.
•First ½ hour of operation
oFollow the starting procedure listed in this manual.
oAvoid prolonged operation at Wide Open Throttle.
•After 1 hour of operation
oCheck for loose bolts and nuts on the bike and retighten as
necessary (proper toque values are listed under Specifications).
oClean the carburetor bowl.
oChange the transmission / clutch lubricant.
•After 8 hours of operation
oChange the fork oil.
oHave 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 loose 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.
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.