Cobra DCX65 2003 Owner's And Service Manual

2003 DCx65

Owners / Service Manual

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1

Cobra Motorcycle MFG., Inc.

11511 Springfield Road
North Lima, Ohio 44452

MCDC2003.1

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 DC65 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.

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Table Of Contents

General Information.........................................................................................................5

Specifications - General..............................................................................................5

Specifications - Torque Values ..................................................................................6

Specifications – Suspension.......................................................................................8

Optional Components......................................................................................................9

Break-In Procedure....................................................................................................10

Starting Procedure.....................................................................................................11

General Tips ................................................................................................................12

Maintenance....................................................................................................................13

Schedule & Tips .........................................................................................................13

M1: Replacing Transmission Lubricant ...................................................................14

M2: Chain adjustment................................................................................................15

M3: Front brake adjustment......................................................................................16

M4: Clutch lever adjustment.....................................................................................16

M5: Rear brake adjustment ......................................................................................17

M6: Air Filter Cleaning ...............................................................................................18

M7: Fork Oil Replacement........................................................................................19

Engine Parts / Service...................................................................................................20

ES1: Top End Parts ...................................................................................................20

ES2: Bottom end & transmission.............................................................................20

ES3: Clutch and Shifter components......................................................................21

ES4: Ignition................................................................................................................24

ES5: Cooling System.................................................................................................25

ES6: Fuel & Air System.............................................................................................25

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ES7: Exhaust ..............................................................................................................26

Tuning ..............................................................................................................................27

Tuning 1: Carburetor..................................................................................................27

Jetting Decisions ....................................................................................................27

Jetting Changes......................................................................................................30

Tuning 2: Suspension................................................................................................34

1 Suspension Guidelines ......................................................................................35

2 Proper Suspension Adjustments for Your Rider............................................36

3 Symptoms of Incorrect Suspension Adjustment............................................40

4 Proactive Suspension Adjustments .................................................................41

5 How to Adjust the Suspension ..........................................................................42

6 Suspension Reference.......................................................................................43

Troubleshooting..............................................................................................................44

Index.................................................................................................................................45

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General Information

Specifications - General

Items DC65

Dimensions

Wheelbase 44.75” (1136 mm)
Wheel size 14” (356 mm) front, 12” (305 mm) rear
Seat height

Engine

Type 2-stroke, single cylinder, reed valve
Cooling system Liquid-cooled
Displacement 64.8 cc (3.95 Cubic inches)
Bore and stroke 43 mm x 44.6 mm
Ignition system Electronic
Spark plug Splitfire SF406B

Gap 0.023” – 0.025” (0.58 – 0.64 mm)

Fuel type Sunoco MO2X or 93 octane pump gasoline

Oil type Cobra Venom 2-cycle Race Oil
Fuel / oil mix ratios 32:1 to 40:1
Ignition timing 0.050”
Carburetion 28 mm PWK style

OTHER RACE FUELS ARE NOT RECOMMENDED

Slow (Pilot) jet 38

Float height 19 mm + 0. 5mm (0.75” + 0.020”)

Transmission

Speed Six speed
Clutch Manual hydraulic
Final drive ratio 13/46 T
Transmission / clutch oil type 85W 90 Gear Lubricant

5

Main jet 128

Jet needle JJH 3rd position from the top

Quantity 530 ml (18 oz)

Chassis

Front tire 60/100 x 14

Pressure 10 - 15 psi.

Rear tire 80/100 x 12

Pressure 10 - 15 psi.

Front fork Cobra USD 35 mm

Fork oil type SAE 5 weight

Fork oil amount

Fork oil level

4 oz (118 ml)

Specifications - Torque Values

ENGINE Fastener

Cylinder head nuts 9.2 110 12 ¼” x 20

Engine oil drain 3 36 4 8 x 1.25

Engine oil fill 2 24 2.7 14 x 1.0

Spark Plug (SP) (SP) (SP)

Crank case half 5 60 6.8 6 x 1.0

Crank case cov er 5 60 6.8 6 x 1.0

Flywheel rotor nut 40 480 54 10 x 1.25 (G)

Torque Value

ft-lb in-lb Nm

Remarks

14 x 1.25

Size &

Clutch hub 40 480 54 10 x 1.25 (G)

Units of mm unless otherwise specified

(G) denotes the use of wicking / bearing retainer (green) thread locking agent to

applied to the mating surfaces of the two components but not the threads.
(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.

6

CHASSIS Fastener

Front axle nut 25 300 34 12 x 1.25

Front brake caliber 22 264 30 8 x 1.25

Front brake rotor 6 72 8 6 x 1.0 (B)

Triple clamp bolts 6 72 8 6 x 1.0

Fork cap 5 60 6.7 1.25” x 18

Steering head 30 350 40 1.0” x 12 (R)
Handle bar mounts 15 177 20 8 x 1.25
Handle bar clamps 15 177 20 8 x 1.25

Front engine mount 22 265 30 8 x 1.25

Rear brake lever pivot 10 120 13.6

Subframe fasteners 22 265 30 8 x 1.25

Upper shock mount 40 480 54 10 x 1.5

Torque Value

ft-lb in-lb Nm

Size &

Remarks

8 x 1.25

Lower shock mount 40 480 54 10 x 1.5

Swingarm pivot 21 250 28 14 x 2.0

Rear axle nut 25 300 34 12 x 1.25

Rear sprocket bolts 13 160 18 8 x 1.25 (B)

Rear brake caliper bolts 22 264 30 8 x 1.25

Rear brake rotor bolts 6 72 8 6 x 1.0 (B)

Units of mm unless otherwise specified

(R) designates that the application requires the use of high strength (red) thread

locking agent applied to the threads.
(B) designates that the application requires the use of medium strength (blue)

thread locking agent applied to the threads.

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Specifications – Suspension

Fork Oil

Viscosity

Oil Height

(amount)

Fork Spring

Shock Spring

Preload height

Rebound

Damping (clicks

from full damp)

Compression

Damping (clicks

from full damp)

Factory

setting

5 wt

4 oz

(118 ml)

STD.
STD.

Track 1 Track 2 Track 3 Track 4

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Optional Components

• Carburetor jets

• Sprockets

o Front
o Rear

• Suspension Springs
Weight of Rider (lb) Fork Spring Shock Spring

Less than 51 - SCDC0285 (285 lb/in)

51 - 60 KCDCSP01

Greater than 60 KCDCSP02

SCDC0350 (350 lb/in)

• Suspension Valving

Damping Rate Fork Valving

Soft (fast) KCDCBV01 KCDCMV01 SCDCOH01A

Standard KCDCBV02 KCDCMV02 SCDCOH01

Hard (slow) KCDCBV03 KCDCMV03 SCDCOH01B

• Flywheel weights

o Middle weight #ECDC0200
o Heavy weight #ECDC0201

(blue, 14 lb/in)

(red, lb/in)

Compression

(base valve)

SCDC0300 (300 lb/in)
SCDC0325 (325 lb/in)

Fork Valving

Rebound

(mid valve)

Shock Valving

(kit)

9

Break-In Procedure

Your Cobra Motorcycle is a close-tolerance high performance machine and
break-in time is very important for maximum life and performance. The DC65 can
be ridden hard after the first ½ hour break-in time but it is recommend ed 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
93 octane pump gas, or Sunoco MO2X , 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.

• First ½ hour of operation

o Follow the starting procedure 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.
o Replace the fuel filter.

• 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!

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Starting Procedure

Before starting the machine inspect the following:

• Insure that the fuel tank contains an adequate volume of fuel / oil mixture to
complete the distance required. (Sunoco MO2X or 93 octane pump gas with
Cobra’s specially formulated Cobra Venom 2-cycle Race Oil)

• 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.

• Inspect the frame, for;

o Cracks in the metal.
o Cracking paint which might indicate overly stressed material.

• Verify that the handlebars are tight.

• Check the throttle for;

o Smooth operation and sound closing.
o Frayed strands of the cable inside the throttle housing.

• Check for loose bolts and nuts, and re-torque as necessary.

• Verify that the air filter is cl ean and properly saturated with 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. Reaching down to the carburetor, on the left side of the bike, pull up the
black choke knob and rotate it so that it locks in this ‘up’ position.

2. Kick start the engine.

3. Rev the engine in short spurts, turning the throttle no more than 1/4 open
until the engine will run without the choke.

4. Verify a functional engine shut-off switch by shutting off the engine.

5. 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.

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General Tips

1. Always wear a helmet 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 rear brake pedal 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. Some people have found cable ties (zip ties) more favorable for securing

the rear brake line to the swingarm.

8. Also, some people are moving the rear brake line (hose between the

master cylinder and the reservoir) from it’s stock position, to a position
slightly more forward and securing it with a cable tie (zip tie). This moves it
further from the heat of the exhaust pipe.

9. Mare sure that there is adequate free play in both the front lever and rear

brake pedal .

10. Your Cobra Motorcycle has a 12 digit VIN (Vehicle Identification Number).

The first four digits indicate the model and the nineth indicates the model
year (MY).

a. The exception is that ’03 MY DC65 which came out late so the

model year is off by one.

b. Example, DC65-xxx-x2xxx is a 2003 MY DC65.

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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 Inspect the fuel filter for contaminates.
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.

• 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. 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.

2. 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.

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