Cobra PW3 2003 Application guide

2003 PW3
Owners / Service Manual
“CHAMPIONS START HERE”

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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 MCPW2003.4

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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 PW3 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 aperson 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.........................................................................................................4
Specifications -General..............................................................................................4
Specifications -Torque Values ..................................................................................5
Optional Components..................................................................................................6
Break-In Procedure......................................................................................................7
Starting Procedure.......................................................................................................8
General Tips..................................................................................................................9
Maintenance....................................................................................................................10
Schedule & Tips .........................................................................................................10
M1: Replacing Transmission / Clutch Lubricant....................................................11
M2: Chain adjustment................................................................................................12
M3: Front brake adjustment......................................................................................13
M4: Rear brake adjustment ......................................................................................14
M5: Air Filter Cleaning ...............................................................................................14
M6: Fork Oil Replacement........................................................................................15
M7: Clutch Adjustment ..............................................................................................16
Engine Service / Parts...................................................................................................17
ES1: Top End Parts ...................................................................................................18
ES2: Bottom end & transmission.............................................................................19
ES3: Clutch.................................................................................................................22
ES4: Ignition................................................................................................................23
ES5: Cooling System.................................................................................................24
ES6: Fuel & Air System.............................................................................................25
ES7: Exhaust ..............................................................................................................30
Chassis Service / Parts .................................................................................................30
CS1: Wheels & Tires .................................................................................................30
CS2: Suspension........................................................................................................32
Troubleshooting..............................................................................................................36

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General Information
Specifications -General
Items PW3
Dimensions
Wheelbase 35.75” (908mm)
Wheel size 10” (254mm)
Seat height 22” (559 mm) Stock #TCHO0001
23.9” (607 mm) Optional #TCHJ0001
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 ChampionC53, NGK B11EGV
Gap 0.023” –0.025” (0.58–0.64 mm)
Fuel type Sunoco MO2X or 93 octane pump gasoline
OTHER 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 5 mm +0.3mm (0.2” +0.012”)
Transmission
Speed Single
Clutch 3 shoe centrifugal
Final drive ratio 10/46 T
Transmission / clutch oil type Cobra Venom 3 Shoe Clutch Milk, or Dexron III
Quantity 250 ml (8.5oz)

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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
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
Front engine mount bolts 22 264 30 8 x 1.25
Rear engine mount bolts 22 264 30 8 x 1.25
Swingarm pivot bolt 21 250 28 14 x 2
Rear sprocket bolts 18 216 24 7 x 1
Rear axle bolts 25 300 34 12 x 1.25
Rear shock mounts 40 480 54 10 x 1.5
Clutch adjust access plug 10 124 14 12 x 1.25
Units of mm unless otherwise specified

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Optional Components
•Carburetor jets
oMain jets #’s 74, 76, 78, 80, 84, 86, 88
oSlow jets #’s 38, 40, 45,
•Sprockets
oFront sprocket, 11T
oRear sprocket, 39 T –45 T
•Seat –higher seat height 23.9” (607 mm) part # TCHJ0001
•Suspension Springs
Weight of Rider (lb) Fork Spring Shock Spring
Less than 38 (light) KCMZ0012A SCMU0321 (yellow, 320 lb/in)
38 –45 (std) KCMZ0012 SCMU1360 (red, 260 lb/in)
46 to 55 (stiff) KCMZ0012B SCMU1380 (white, 380 lb/in)
Extra stiff SCMU1400 (silver, 400 lb/in)
•Suspension Valving
Damping Rate Fork Valving
Compression
(right)
Fork Valving
Rebound
(left)
Shock Valving
(kit)
Soft (fast) KCMZ0033A KCMZ0032A SCMU0318A
Standard KCMZ0033 KCMZ0032 SCMU0318
Hard (slow) KCMZ0033B KCMZ0032B SCMU0318B

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Break-In Procedure
Your Cobra PW3 is a close-tolerance high performance machine and break-in
time is very important for maximum life and performance. The PW3 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!
Fill the fuel tank with 93 octane pump gas, or Sunoco MO2X without oil. 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.
•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!

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Starting Procedure
Before starting the machine inspect the following:
•Fill the 2-stroke injector oil reservoir with Cobra’s specially formulatedCobra
Venom 2-cycle Race Oil.
•Insure that the fuel tank contains an adequate volume of fuel to complete
the distance required. (Sunoco MO2X or 93 octane pump gas).
•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;
oCracks in the metal.
oCracking paint which might indicate overly stressed material.
•Verify that the handlebars are tight.
•Check the throttle for;
oSmooth operation and sound closing.
oFrayed 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 clean 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. 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. 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 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, OIxxxx3xxx is a 2003 MY PW3.

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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
oFill the 2-stroke injector oilreservoir.
oCheck the air filter (clean and re-oil as necessary).
oInsure the smooth operation of the throttle cable (throttle soundly
‘clacks’ shut).
oCheck for frayed strands of the throttle cable inside the throttle housing
and replace if necessary.
oCheck for adequate tire pressures and adjust if necessary.
oCheck all nuts and bolts for proper torque and re-torque if necessary.
oSpray all moving parts with WD40 or other light oil.
oCheck drive chain for
§Proper tension and adjust if necessary.
§Adequate lubrication and lubricate if necessary.
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 it’s safe limits.
Replace or get properly rewelded as necessary.
oFill the 2-stroke injector oil reservoir with Cobra’s specially formulated
Cobra Venom 2-cycle Race Oil.
•Every 2 hours of operation
oReplace the transmission oil.
•Every 10 hours of operation
oReplace the fork oil.
oHave 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 clampas close to the area
to be welded as possible.

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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.
M1: Replacing Transmission / Clutch
Lubricant
Tools needed:
•250 ml (8.5oz) Cobra Venom 3 Shoe Clutch Milk (Part # MCMUGF01) or
Dexron III Automatic Transmission Fluid
•#3 Phillips screwdriver
•large flat blade screwdriver or coin
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 Phillips screwdriver, remove the oil drain bolt located on the right side
of the engine (figure 1).
Figure 1

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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 drain screw with gasket.
5. Refill oil from oil fill plug 250 ml (8.5oz) Cobra Venom 3 Shoe Clutch Milk
(Part # MCMUGF01), or Dexron III Automatic Transmission Fluid, thru the fill
plug.
NOTE: Leaning the bike over onto it’s left hand side will facilitate the oil filling
procedure.
6. Reapply the oil fill screw, securely, being sure the 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 was forced to put forth this effort because the other available
options and not adequate. Cobra’s specially developed Cobra Venom 3 Shoe
Clutch Milk (Part # MCMUGF01) is the recommended lubricant for your PW3
motorcycle.
M2: Chain adjustment
Tools required for chain adjustment
•Two 19 mm wrenches or sockets
•13 mm wrench or socket
1. Make sure that the rear
wheel is aligned
properly.
2. For proper adjustment,
the chain should have 35
mm (1 3/8”) free
movement just behind
the chain block with no
load on the bike (figure
2)
Figure 2
CAUTION:
Verify that the chain has a minimum of 6mm (1/4”) free movement when the
suspension is collapsed.

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3. If the chain requires adjusting, loosen the axel
with a pair of 19 mm wrenches and tighten the
chain by rotating the adjuster bolts clockwise
(CW) or loosen the chain by rotating the adjuster
bolts (CCW).
4. Retighten the axel bolt to 25 ft-lb (34 Nm).
Figure 3
M3: Front brake adjustment
Tools recommended for front brake maintenance:
•10mm open end wrench
From the brake lever:
1. Loosen the locking nut on the brakelever.
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.
Figure 4, from the brake lever Figure 5, from the brake hub

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M4: Rear brake adjustment
Tools recommended for rear brake maintenance:
•10mm open end wrench
There are 2 adjustments on the brake.
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 remain engaged. If so,
the brake pads will burn up, and need replaced.
M5: Air Filter Cleaning
Tools recommended for air filter maintenance:
•#2 Phillips head screwdriver
•4 mm hex key (Allen)
•Foam filter oil
Procedure
1. Removed the seat with the 4 mm hex key
2. Remove the two Phillips head screws holding the filter to the entrance of the
airbox.
3. Clean the filter in a nonflammable solvent to remove the filter oil.
4. Clean the filter in hot soapy water to remove all dirt particles.
5. Allow to dry thoroughly.
6. Saturate with filter oil and remove excess.
Figure 6, adjust brake lever free height Figure 7, adjust lever ‘free play’

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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 three or more filters in your toolbox.
•1 for practice
•1 for each moto
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.

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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.
M7: Clutch Adjustment
Tools required
6 mm hex key (Allen wrench)
large flat blade screw driver
Process
1. Remove the clutch adjustment access plug (6mm hex key).
Figure 8
2. Using the kick lever, turn the engine over (rotate the crank) until one of the
large flat head screws is visible through the access hole (this flat head screw
is one of the three adjusters).
NOTE: Turning the adjusting screw Counter Clock Wise (CCW) will allow the
shoe to engage at a lower RPM, this is the direction you should adjust to
compensate for shoe wear. Alternatively, a Clock Wise (CW) adjustment of the
screw will allow the clutch to engage at a higher RPM.
3. Subsequently use the kick lever to rotate the crank and expose the other two
clutch shoe adjusters and adjust them by the same amount.
CAUTION:
Be sure to adjust each of the three shoe adjustors by thesame amount.
4. Reinstall the clutch adjust access plug (10 ft-lb, 14 Nm).

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Engine Service / Parts
Factory trained technicians with precision gauging and proper assembly fixtures
carefully assemble all Cobra engines to specific clearances. If you feel you have
the skills, and the appropriate tools, to perform the following service tasks please
follow the instructions closely. The part numbers are listed throughout to help you
when ordering parts from your local Cobra dealer.
If you don’t feel comfortable with the service work, simply take your engine out of
the frame and sent it to:
Cobra Precision Engines
11511 Springfield Road
North Lima, Ohio 44452
Cobra’s technicians will go through the entire engine, replacing gaskets, bolts,
any old part that is worn. The engine will be rebuilt using the same precision
gauging and assembly fixtures as when it was assembled new. Before leaving,
the engines performance will be measured on a dynamometer to ensure that
your engine is operating at its highest potential. All this for one low nominal fee,
plus cost of parts. Call [phone] for details.

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ES1: Top End Parts
Figure 9, Top End Components
REF NO PART NO DESCRIPTION
1 ECMOTE01 CYLINDER -CHROME
2 ECMOTE02 PISTON KIT -SINGLE RING
3 HCBC0603 6X30 CAP SCREW
4 HCNF0601 FLANGED NUT 6MM
5 ECMOTE05 CYLINDER HEAD
6 ZCMOTE06 CYLINDER HEAD O-RING
7 ECMU0026 6MM DOWEL
9 ECMOTE09 CYLINDER HEAD STUD BOLT 6MM
10 ZCMOTE10 BASE GASKET
11 ZCMOTE11 O-RING -EXHAUST FLANGE
12 ECMU0056 PISTON RING -CAST
13 ECMU0076 WRIST PIN
14 ECMUSR04 SNAP RING-FRANCO PISTON

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ES2: Bottom end & transmission
Figure 10, bottom end components
REF NO PART NO DESCRIPTION
1 ECMOBE01 CASES -COMPLETE SET
2 ECMOBE02 OUTPUT BEARING
3 ECMOBE03 OUTPUT BEARING -SNAP RING
4 ECMOBE04 PRECISION BEARING
5 ECMOBE05 CRANK SEAL
6 ECMU0016 CRANK BEARING
7 ECMOBE07 CRANKSHAFT COMPLETE
8 ECMOBE08 FLYWHEEL KEY
9 ECMU0077 WRIST PIN BEARING
10 HCBC0660 6X60 CAP SCREW
11 HCBC0607 6X50 CAP SCREW
12 ZCMOBE12 CRANKCASE GASKET
13 ECMOBE13 OUTPUT SEAL
14 ECMOBE14 ROD WITH WRIST PIN AND BEARING
15 S6 V/EC.+COM. SET OF SEAL
16 ZKMOBE16 GASKET KIT
17 ECMOBE17 DOWEL PIN -CASE
18 ECMOBE18 CASE VENT PIPE