Cobra 2004 cm50 Owner's Manual
2004 CM50
Owners / Service / Parts
“CHAMPIONS START HERE”
For parts orders contact your local dealer
To locate your closest Cobra dealer
log on to
www.cobramotorcycle.com
or call
(330) 549-9600
If you need technical assistance
contact your local dealer or call
the Cobra Technical Support Hotline at
(330) 549-9603
Cobra Motorcycle MFG., Inc.
11511 Springfield Road
North Lima, Ohio 44452
MCCM2004.2
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 CM50 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.
2
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
3
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
I gnition..........................................................................................................................53
Cooling System...........................................................................................................55
ES6: Fuel & Air System.............................................................................................59
Exhaust........................................................................................................................62
Wheels & Tires ...........................................................................................................63
CS2: Suspension ........................................................................................................65
Troubleshooting..............................................................................................................66
Index.................................................................................................................................67
4
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) Option al # 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
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
RACE FUELS ARE NOT RECOMMENDED
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
5
Quantity 235 ml (8.0oz)
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
6
Specifications - Torque Values
Torque Value
Fastener ft-lb in-lb Nm
Cylinder head nuts 9.2 110 12 ¼”
Crankcase bolts 6.6 80 9 6 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 x 1.25***
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
Size &
Remarks
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.
7
Optional Components
Call your dealer, or the factory, for details
• Carburetor jets
• Sprockets
o Front
o Rear
• 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)
Soft (fast) KCMZ0033A KCMZ0032A SCMUOH07
Standard KCMZ0033 KCMZ0032 SCMUOH08
Hard (slow) KCMZ0033B KCMZ0032B SCMUOH09
Fork Valving
Rebound
(left)
Shock Valving
(kit)
8
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
o Follow the starting procedu re listed in this manual.
o 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 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.
9
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 do not have improper wear.
• Verify that the handlebars are tight.
• Check the throttle for smooth operation and sound closing.
• 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 Cobra’s
specially formulated Cobra Venom 2-cycle Race 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.
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 when it's cold or slightly warmed up. 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. Make sure your
engine is properly warmed up before racing.
10
General Tips
1. Always wear a hel met and other protective riding gear.
2. 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.
3. Make sure your riders’ foot is not resting on the foot brake while they are
riding.
4. Evaluate the bikes jetting only after it has been warmed up to race
temperatures.
5. A properly maintained machine is safer, faster, and more fun to ride.
6. When washing the bike, be careful to not directly aim the hose at the
bottom edge of the seat, or water is apt to enter the airbox.
7. 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).
a. Example, CMxxxx4xxx is a 2004 MY CM50.
11
Maintenance
Schedule & Tips
It is important that you adhere to this maintenance schedule so as to promote the
longevity of your Cobra Motorcycle.
• Between each ride
o Check the air filter (clean and re-oil as necessary).
o Insure the smooth operation of the throttle cable (throttle soundly
‘clacks’ shut).
o Check for frayed strands of the throttle cable inside the throttle housing
and replace if necessary.
o Check for adequate tire pressures and adjust if necessary .
o Check all nuts and bolts for proper torque and re-torque if necessary.
o Spray all moving parts with WD40 or other light oil.
o Check drive chain for
§ Proper tension and adjust if necessary.
§ Adequate lubrication and lubricate if necessary.
o Insure that the ignition stator and rotor are clean and dry.
o Check the frame for cracks in the metal or cracks in the paint that
might indicate that the metal has been stressed beyond it’s safe limits.
Replace or get properly rewelded as necessary.
o Inspect the rear sprocket damper plate for bending or warping.
Straighten or replace if more than 1/16” (1.6 mm) from flat.
• Every 2 hours of operation
o Replace the transmission oil.
• Every 10 hours of operation
o Replace the fork oil.
o Have the shock oil replaced by a Certified Cobra Mechanic.
CAUTION:
1. 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.
2. 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.
12
Be sure the fuel tank and carburetor have been removed and safely located
away from the welding process.
3. 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.
4. If your kick-starter lever does not return to the rubber bumper, use WD-40
or light penetrating oil under the plastic cover behind the spring on the
shaft. The shaft is a very close fit to the case and also has an O ring in it
and is difficult to get lubrication to which may cause binding. If it does not
loosen up, remove the kick-starter cover and kicking assembly. Grease the
shaft.
M1: Replacing Transmission / Clutch
Lubricant
Tools needed:
• 225 ml (7.6 oz) Cobra Venom 3 Shoe Clutch Milk (Part # MCMUGF01), or
Dexron III Automatic Transmission Fluid.
• 13 mm combination wrench
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 ‘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. Lean bike against something or set on stand with oil drain hole.
3. Using a 13 mm wrench, remove the oil drain bolt located on the right side of
the engine, on the clutch cover, near the brake lever (Item 2, figure 1).
13
Figure 1
NOTE: You may need to adjust the brake pedal (up or down) to gain access to
the drain bolt.
4. After it has drained, reinstall the bolt being sure that the copper gasket is in
place. Torque to 15 Nm (11 ft-lb).
5. Reapply oil from oil fill plug 235 cc Cobra Venom 3 Shoe Clutch Milk, or
Dexron III Automatic Transmission Fluid, thru the fill plug.
NOTE:
Lean bike over onto it’s left hand side so that the clutch cover is up unless you
have a squeeze bottle.
6. Reapply the oil fill bolt, hand tight, being sure the fiber gasket is in place.
CAUTION:
Cobra has spent considerable time and money developing the proper lubrication
to handle the harsh environment of the automatic clutch and transmission of this
motorcycle. Cobra’s specially developed Cobra Venom 3 Shoe Clutch Milk (Part
# MCMUGF01) was formulated to provide superior lubrication and cooling
capability over extended periods of time and is the recommended lubricant for
your Cobra motorcy cle.
M2: Chain adjustment
Figure 2
14
1. Make sure that the rear
wheel is aligned properly.
2. Push down on the seat,
compressing the suspension down to where the
chain is tightest.
3. The chain should not be
too tight but not too
loose. A minimum of 2.5
in. of slack should be
between the swing arm
and the chain.
M3: Front brake adjustment
Tools recommended for front brake maintenance:
• 10mm open end wrench
Figure 3, from the brake lever Figure 4, from the brake hub
From the brake lever:
1. Loosen the locking nut on the brake lever.
2. Adjust the bolt to desirable position.
3. Tighten the locking nut.
From the brake hub:
1. Loosen the 10mm nut on the hub.
2. Adjust the brake cable to desirable position
3. Tighten the 10mm nut.
CAUTION:
If you tighten the front brake up too much, the brakes may hang up causing the
brake pads to wear incorrectly and prematurely.
M4: Rear brake adjustment
Tools recommended for rear brake maintenance:
• 10mm open end wrench
There are 2 adjustments on the brake.
Figure 5, adjust brake lever free height Figure 6, adjust brake lever ‘free play’
15
From the brake lever:
4. Loosen the 10mm nut on the back of the brake pedal.
5. Adjust the bolt to desirable position
6. Tighten the 10mm nut.
From the brake hub:
1. Adjust the wing nut up to desirable position.
CAUTION:
If you tighten the wing nut up too much, the brakes may hang up. If so, the brake
pads will burn up, and need replaced.
M5: Air Filter Cleaning
Tools recommended for air filter maintenance:
• Flat screwdriver
• 4 mm hex key (Allen)
• Foam filter oil
Procedure
1. Removed the seat with the 4 mm hex key
2. Remove the filter/air inlet boot from the back of the carburetor with a flat
screwdriver
3. Pull the filter / boot assembly back, up, and out the top of the airbox.
4. Clean the filter in a nonflammable solvent to remove the filter oil.
5. Clean the filter in hot soapy water to remove all dirt particles.
6. Allow it to dry thoroughly.
7. Saturate with filter oil and remove excess.
8. Reinstall the filter / boot assembly to the carburetor with the letters “CM”
visible from the side.
Do not clean the air filter with gasoline or other highly volatile petroleum product.
Diesel fuel or kerosene would be preferred but caution should still be taken. Hot
soapy water works well.
NOTE:
The Cobra is equipped with a special designed Air box. It is very important to
keep the air filter clean and properly oiled with high quality water-resistant foam
filter oil. It’s very important to oil your filter consistently each time because varied
amounts of oil will change your carburetor jetting.
NOTE:
Make sure you change or clean your filter after each moto. We recommend
carrying multiple filters in your toolbox, one for each practice session and moto.
16
M6: Fork Oil Replacement
Tools required
• 5 & 6 mm Allen wrench
• 19 mm wrench or socket (two required)
• Spring clip remover
Disassembly
1. Remove the front wheel.
2. Remove the fork legs from the triple clamps.
3. Perform the following on one leg at a time.
4. Using your hands, remove the black rubber plug from the top of the fork leg
exposing the white plastic cap.
5. Secure the fork leg assembly in a vice by gripping the leg across the flats
through which the axle bolt goes through.
6. Depress the white plastic cap inwards (down) and remove the wire spring clip
from its groove.
7. Remove the white cap, the fork spring preload sleeve, and the fork spring.
NOTE: Depressing the fork leg will facilitate removing the white cap.
8. The fork can now be turned upside down and drained.
Assembly
1. Fill the leg with 200 cc (6.8 oz) 20 wt fork oil.
2. Standard fork oil level is 70 mm (2.75”) from the top edge with the fork
collapsed.
NOTE: Remove the preload sleeve but leave the spring in for the measurement.
3. Install the preload sleeve.
4. Install and depress the white cap while installing the spring clip.
5. Fork may be reinstalled.
17
Parts
Parts – Airbox and Inlet System
Figure 7
Airbox and Inlet System
REF # PART # DESCRIPTION
1 ZCMU0032 GASKET – REED TO CYLINDER
2 ECKG0205 REED VALVE
3 ZCMU0031 GASKET – MANIFOLD TO REED
4 ECKG0203 INLET MANIFOLD
5 HCWF0601 6MM FLAT WASHER
6 HCBC0625 M6X25 SOCKET HEAD CAP SCREW
7 MCKGHO01 HOSE CLAMP – CARBURETOR TO MANIFOLD
8 RACM0002 CARBURETOR 14MM
9 FCMU0067 THROTTLE CABLE
10 RCCM1301 VELOCITY STACK
11 MCKGHO01 HOSE CLAMP – AIR BOOT TO CARBURETOR
12 RCMU0403 AIR FILTER WITH BOOT
13 RCMU0405 AIR BOX – CM
14 HCBF0416 M6X16 FLANGE HEAD BOLT (2 REQ’D)
15 RCMU1407 BRACKET – MUD FLAP
16 RCMU0406 MUD FLAP – CM
18
Parts – Bars and Controls
Figure 8
Bars and Controls
REF # PART # DESCRIPTION
1 FCMU0066 THROTTLE ASSEMBLY
2 FCMU0068 THROTTLE COVER
3 TCMU0008 GRIPS (SET OF TWO)
4 FCMU0067 THROTTLE CABLE
5 FCMU0033 KILL SWITCH ASSEMBLY
6 KCMZ0001 M8X50 SOCKET HEAD CAP SCREW (4 REQ’D)
7 KCMZ0003 LOWER HANDLE BAR CLAMP (2 REQ’D)
8 KCMZ0002 TOP HANDLE BAR CLAMP (2 REQ’D)
9 TCMU0019 HANDLEBAR - ALUMINUM
11 BCMU0100 BRAKE LEVER / PERCH ASSEMBLY WITH ADJUSTER
13 BCMU0108 FRONT BRAKE CABLE
19
Parts Carburetor
Figure 9
Carburetor
REF. # PART # DESCRIPTION
RCCM0001 COMPLETE CARBURETOR 14MM
1 RCMU0305 CARB SLIDE
2 RCMU0601 NEEDLE
3 RCMU0002 ATOMIZER
4 RCMU0092 MAIN JET
5 RCMU0055 PILOT JET
6 CHOKE JET
7 RCMU0301 FLOAT
8 RCMU0102 RUBBER CABLE CAP SEAL
9 RCMU0003 CABLE ADJUSTER
11 RCMU0006 TOP CARB SCREW
12 RCMU0106 CARB TOP
13 ZCMU0007 TOP CARB GASKET
14 RCMU0004 SLIDE SPRING
15 RCMU0205 NEEDLE RETAINER PLATE
16 RCMU0007 NEEDLE CLIP
17 RCMU0204 CHOKE ASS’Y. 2001 CM
20 RCMU0009 FUEL MIXTURE SCREW
21 RCMU0011 IDLE ADJUSTMENT SCREW
25 RCMU0103 FLOAT BOWL GASKET
26 RCMU0107 FLOAT NEEDLE
27 RCMU0012 DIFFUSER
28 RCMU0016 FLOAT RETAINER PIN
29 RCMU0106 FLOAT BOWL
30
RCMU0201 BOTTOM FLOAT SCREW
31
33 RCCM1301 VELOCITY STACK
RCCM0314 14MM CARB RESTRICTOR
20
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