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Cobra Moto 2008 X50JR Service Manual

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Summary of Contents for Cobra Moto 2008 X50JR

  • Page 2 For parts orders contact your local dealer To locate your closest Cobra dealer log on to www.cobramotorcycle.com or call (517) 437-9100 If you need technical assistance contact your local dealer or call the Cobra Technical Support Hotline at (517) 437-9100 Cobra Motorcycle MFG., Inc.
  • Page 3 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 CX50JR IS A COMPETITION MODEL ONLY AND IS NOT MANUFACTURED FOR, NOR SHOULD IT BE USED ON PUBLIC STREETS, ROADS OR HIGHWAYS.

  • Page 4: Table Of Contents

    Table Of Contents General Information ....................5 Specifications - General ..................5 Specifications - Torque Values................6 Optional Components..................7 Break-In Procedure ...................8 Starting Procedure ....................9 Maintenance .......................10 Tips .........................10 Schedule ......................11 Replacing Transmission / Clutch Lubricant .............12 Proper Chain adjustment.................14 Air Filter Cleaning....................14 Fork Oil Replacement..................16 Frictional Drive (CFD)..................17 Parts ........................18...
  • Page 5 Parts – Front Brakes ..................33 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 Base Gasket Selection ................41 Engine Removal ..................43 Complete Engine Disassembly Procedure ..........44 Top End Disassembly Procedure ..............44...

  • Page 6: General Information

    General Information Specifications - General Items CX50 JR Dimensions Wheelbase 35.75” (908mm) Wheel size 10” (254mm) Seat height 23.9” (607 mm) Engine Type 2-stroke, single cylinder, reed valve Cooling system Liquid-cooled Coolant Liquid Performance Mini Coolant or Antifreeze Displacement 49.8 cc Bore and stroke 39 mm x 41.7 mm, “V”...

  • Page 7: Specifications - Torque Values

    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 Specifications - Torque Values Torque Value...

  • Page 8: Optional Components

    Rear Sprocket Bolts M7 X 1.0** Axle nuts M12 X 1.25 * Apply high strength thread locking agent when installing **Apply medium strength thread locking agent when installing (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...

  • Page 9: Break-In Procedure

    Break-In Procedure Your Cobra CX50 JR is a close-tolerance high performance machine and break- in time is very important for maximum life and performance. The CX50 JR 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.

  • Page 10: Starting Procedure

    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.

  • Page 11: Maintenance

    CAUTION: Never rev an engine full throttle when it's cold or slightly warmed up. Also, for best clutch performance, warm up the bike before taking off. 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.

  • Page 12: Schedule

    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, CMxxxx7xxx is a 2007 MY CX50 JR. Schedule • Between each ride Check the air filter (clean and re-oil as necessary).

  • Page 13: Replacing Transmission / Clutch Lubricant

    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.
  • Page 14 Figure 1 4. After it has drained, reinstall the plug, being sure that the gasket is in place. 5. Reapply oil from oil fill plug 235 cc (8.0 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.

  • Page 15: Proper Chain Adjustment

    Proper Chain adjustment Tools required for chain adjustment • 19 mm wrench or socket • 13 mm wrench or socket 1. Make sure that the rear wheel is aligned properly. 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)
  • Page 16 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. 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.

  • Page 17: Fork Oil Replacement

    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.

  • Page 18: Frictional Drive (Cfd)

    Frictional Drive (CFD) The Cobra Frictional Drive (CFD) is essentially a slip clutch that dissipates torque spikes transmitted from the rear wheel to the rest of the drive line and engine. Instead of these torque spikes potentially damaging internal components, the CFD allows the transmission to slip with respect to the engine.

  • Page 19: Parts

    Parts Parts – Airbox and Inlet System Figure 7 Airbox and Inlet System REF # PART # DESCRIPTION ZCMU0132 GASKET – REED TO CYLINDER ECKG0202 REED BLOCK ASSEMBLY Not Shown ECKG0205 REEDS REPLACEMENT ECKG0203 INLET MANIFOLD HCWF0601 6MM FLAT WASHER HCBC0625 M6X25 SOCKET HEAD CAP SCREW MCKGHO04...

  • Page 20: Parts - Bars And Controls

    Parts – Bars and Controls Figure 8 Bars and Controls REF # PART # DESCRIPTION FCMU0066 THROTTLE ASSEMBLY FCMU0068 THROTTLE COVER TCMU0008 GRIPS (SET OF TWO) FCMU0019 THROTTLE CABLE FCMU0033 KILL SWITCH ASSEMBLY KCMZ0001 M8X50 SOCKET HEAD CAP SCREW (4 REQ’D) KCMZ0003 LOWER HANDLE BAR CLAMP (2 REQ’D) KCMZ0002...

  • Page 21: Parts - Carburetor

    Parts - Carburetor Carburetor REF. # PART # DESCRIPTION RCCM0001 COMPLETE CARBURETOR 14MM RCMU0305 CARB SLIDE RCMU0601 NEEDLE RCMU00 ATOMIZER AU2.62 RCMU00xx MAIN JET, xx denotes size Figure 9 RCMU00xx PILOT JET, xx denotes size CHOKE JET RCMU0301 FLOAT RCMU0102 RUBBER CABLE CAP SEAL RCMU0003 CABLE ADJUSTOR...

  • Page 22: Parts - Coolant System

    Parts – Coolant System Figure 10 Coolant System REF # PART # DESCRIPTION ECMU0061 RADIATOR WITH CAP MCMUHO02 RADIATOR HOSE LEFT MCMUCL07 HOSE CLAMP ECHA0003 MOUNTING BRACKET – RADIATOR BOTTOM HCBC0607 M6X50 SOCKET HEAD CAP SCREW HCNL0601 6MM LOCK NUT MCKGGR00 GROMMET –...

  • Page 23: Parts - Electrical System

    Parts – Electrical System Figure 6 Electrical System REF # PART # DESCRIPTION IAMU0005 COIL W/SPARK PLUG CAP ECMU0065 SPARK PLUG, CHAMPION (8339-1) ECMU0067 OPTIONAL HOTTER PLUG (8332-1) ECMU0066 OPTIONAL COLDER PLUG (8904-1) FCMU0033 KILL SWITCH ASSEMBLY HCBC0516 SCREW, M5 X 16 (2 PER) HCCN0000 5MM CLIP NUT (2 PER) ICMU0018...

  • Page 24: Parts - Engine - Bottom End And Transmission

    Parts – Engine – Bottom End and Transmission Figure 7A Engine Bottom End and Transmission REF # PART # DESCRIPTION EKMU0023 ENGINE CASE SET W/B&S 50 07 EKMU0023 ENGINE CASE SET W/B&S 50 07 ZCMU0601 GASKET, CRANKCASE CENTER HCBC0605 6X40MM SOCKET HEAD CAP SCREW (6 REQ’D) HCBC0608 6X55MM SOCKET HEAD CAP SCREW (1 REQ’D) HCBC0606...

  • Page 25: Parts - Engine Clutch And Kicker

    Parts – Engine Clutch Kicker Figure 7B Engine – Clutch and Kick Starter REF # PART # DESCRIPTION CAMU0005 CLUTCH COMPLETE CAMU0013 CLUTCH SHOES (SET OF 3) WITH BOLT & WASHERS CCMU0029 CLUTCH ARBOR CAMU0010 SPRINGS, WASHER & BOLT (SET OF 3) HCBS0004 CLUTCH BOLT (3 REQ’D) ECMU0018...

  • Page 26: Parts - Engine - Water Pump

    Parts – Engine – Water Pump Figure 7C Engine – Ignition and Water Pump REF # PART # DESCRIPTION EKMU0001 WATER PUMP KIT ECKG0142 SHAFT, WATER PUMP ECKG0072 BEARING, WATER PUMP ECKG0074 SEAL, WATER PUMP SHAFT ECKG0073 IMPELLER, WATER PUMP ECKG0004 RETAINER, WATER PUMP ASSEMBLY HCBC1512...

  • Page 27: Parts - Engine - Top End

    Parts – Engine – Top End Figure 7D Engine – Top End REF # PART # DESCRIPTION ECMU0129 CYLINDER (INCLUDES PISTON, RINGS, PIN & CLIPS) BASE GASKET 0.015” (0.4mm thick) For other Base Gaskets refer to ZCKG0501 Base Gasket Selection section of this manual ECMU0060x PISTON KIT (“x”...

  • Page 28: Parts - Exhaust System

    Parts – Exhaust System Figure 8 Exhaust System REF # PART # DESCRIPTION XCCM2004 CX50 OI EXHAUST PIPE ZCMOTE11 O-RING – EXHAUST (2 REQ’D) XCMU0005 SPRING – EXHAUST SHORT XCMU0028 PIPE / SILENCER SEAL MCMUGR03 MOUNTING GROMMET (2 REQ’D) TCKG0001 SPACER HCBF0625 M6X25 FLANGE HEAD BOLT...

  • Page 29: Parts - Forks & Triple Clamps

    Parts – Forks & Triple Clamps Figure 9 Front Forks and Triple Clamp REF # PART # DESCRIPTION KCMZ0029 OUTER FORK LEG – RIGHT (NON BRAKE) SIDE KCMZ0131 OUTER FORK LEG ASSY – RIGHT WITH SEAL & SWIPER NOT SHOWN KACM005R FORK LEG COMPLETE –...

  • Page 30: Parts - Forks - Leg Assembly

    Parts – Forks – Assembly Figure 10 REF # PART # DESCRIPTION KCMZ0004 FORK PLUG – BLACK KCMZ0007 SNAP RING FOR FORK CAP KCMZ0008 INNER FORK CAP - WHITE KCMZ0009 O-RING UNDER FORK CAP KCMZ0111 PRELOAD SLEEVE KCMZ0012 FORK SPRING KCMZ0013 SWIPER KCMZ0014...

  • Page 31: Parts - Frame - Mounting Hardware I

    Parts – Frame – Mounting Hardware I Figure 11 Frame – Engine, Tank, and Pipe Mounts, Brake Snake REF # PART # DESCRIPTION FAMU0004 FRAME 2007 CX50 JR HCBH1403 SWINGARM BOLT HCNL1402 SWINGARM LOCK NUT (M14X1) HCBH0880 M8X80 SOCKET HEAD CAP SCREW HCNL0801 8MM LOCKNUT MCMUGR06...

  • Page 32: Parts - Frame - Mounting Hardware Ii

    Parts – Frame – Mounting Hardware II Figure 12 Frame – Seat, Fender, Right Side Panel, Brake Pedal, Silencer & Shock Mounts REF # PART # DESCRIPTION FAMU0004 FRAME 2007CX50 JR HCBB0635 M6X35 BUTTON HEAD CAP SCREW HCHA0003 6MM CLIPNUT HCBF0620 M6X20 FLANGE HEAD BOLT HCNF0602...

  • Page 33: Parts - Frame - Mounting Hardware Iii

    Parts - Frame – Mounting Hardware III Figure 13 Frame – Radiator, Footpeg, Chain Roller, and Airbox Mounts REF # PART # DESCRIPTION FAMU0004 FRAME 2007 CX50 JR ECHA0003 MOUNTING BRACKET – RADIATOR BOTTOM HCBC0607 M6X50 SOCKET HEAD CAP SCREW HCNL0601 6MM LOCK NUT MCKGGR00...

  • Page 34: Parts - Front Brakes

    Parts – Front Brakes Figure 14 Front Brakes REF # PART # DESCRIPTION BAKG0003 FRONT BRAKE ASSEMBLY BCKG0030 HOSE – BRAKE FRONT BCKG0023 ALLOY BRAKE LEVER BCKG0024 BRAKE PERCH & MASTER CYLINDER ASSY W/ LEVER BCKG0029 CALIPER – FRONT BKKG0001 BRAKE PADS, WITH “E”...

  • Page 35: Parts - Front Wheel

    Parts – Front Wheel Figure 15 Front Wheel REF # PART # DESCRIPTION WACJ0001 WHEEL WITH BEARINGS (NO TIRE & TUBE) ’08 SPOKE STYLE WCMU0250 FRONT TIRE 10X2.50” WCMUTU10 TUBE 10” WCMU0014 FRONT AXLE HCWF1202 WASHER – AXLE WCCJ0002 WHEEL SPACER LEFT (SHORT) WCMU0120 BEARING –...

  • Page 36: Parts - Plastic Bodywork & Seat

    Parts – Plastic Bodywork & Seat Figure 16 Plastic and Seat REF # PART # DESCRIPTION NOT SHOWN TCCJ2008 GRAPHIC KIT 2008 CM TCHA0107 FRONT FENDER NOT SHOWN HCBF0616 FENDER BOLT, M6X16 FLANGE HEAD (4 REQ’D) TCMU0005 NUMBER PLATE – FRONT NOT SHOWN HCBF0625 M6X25 FLANGE HEAD BOLT –...

  • Page 37: Parts - Rear Brake

    Parts – Rear Brake Figure 17 Rear Brake System REF # PART # DESCRIPTION BCCM0002 BRAKE PEDAL W/ TEETH BCMU0008 CABLE – BRAKE SNAKE BCMU0009 CRIMP – BRAKE SNAKE HCBB0803 M8X40 BUTTON HEAD SCREW HCNL0801 8MM LOCK NUT HCBH0602 M6X25 HEX HEAD BOLT (BRAKE STOP ADJUST) HCNS0601 6MM NUT BCCM0105...

  • Page 38: Parts - Rear Wheel

    Parts – Rear Wheel Figure 18 Rear Wheel REF # PART # DESCRIPTION WACJ0002 WHEEL W / BEARINGS, ’08 SPOKE STYLE WCMU0275 TIRE – REAR 10X2.75” WCMUTU10 TUBE – 10” PCMU01XX REAR SPROCKET –NO DAMPER ALUM, XX DENOTES TEETH WCMU0016 REAR AXLE HCPA0002 AXLE HEAD FIXING PLATE...

  • Page 39: Parts - Shock

    Parts – Shock Figure 19 REAR SHOCK REF# PART # DESCRIPTION SACM2007 SHOCK ABSORBER SCMUOH05 SPRING – STANDARD (285 lb/in) SCMUOH04 SPRING – LIGHT (275 lb/in) SCMUOH06 SPRING – HEAVY (295 lb/in) HCBF1040 M10X40 FLANGE HEAD BOLT...

  • Page 40: Parts - Swingarm Assembly

    Parts – Swingarm Assembly Figure 20 Swingarm REF # PART # DESCRIPTION GACM2004 SWINGARM ASSEMBLY (CONTAINS ITEMS 1 - 13) GAMU0004 SWINGARM GCMU0001 SWINGARM BUSHING (SINGLE PIECE) GCMU0009 SPACER - PIVOT TUBE GCMU0017 CHAIN GUARD HCFH0516 M5X16 FLAT HEAD SCREW HCWF0501 5MM FLAT WASHER HCNL0501...

  • Page 41: Service

    Service Trained technicians with precision gauging and proper assembly fixtures carefully assemble all Cobra engines to specific tolerances. 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.

  • Page 42: Base Gasket Selection

    Shut off the fuel petcock. Install the compression gauge into the spark plug hole. Hold the throttle to wide open, and kick repeatedly (approximately 20 times) or until the gauge reading does not increase in value with each kick. Base Gasket Selection Tools required •...
  • Page 43 0.035 ZCMU0709 ZCMU0015 0.039 ZCMU0710 ZCMU0016 NOTE Tolerances will affect the actual gasket thickness’. If during the course of the maintenance more parts than the base gasket are changed, the squish clearance should be measured, and possibly a different base gasket will be required. The easiest way to measure squish clearance is with 1mm to 1.5mm thick flexible solder wire (available through most popular electronic stores).

  • Page 44: Engine Removal

    Upon completion, your final assembly squish clearance should agree with the chart below Figure 22 Engine Removal To service the bottom end and transmission, the engine must be removed from the frame. Tools required • 10, 11, 13, 22 mm wrench •...

  • Page 45: Complete Engine Disassembly Procedure

    Remove front engine mount bolt (13 mm socket, 6 mm hex key). Remove the swingarm bolt (22mm socket). NOTE: Only drive the swingarm bolt far enough to clear the engine, leave it holding the one side of the swingarm to the frame Remove the engine from the right side of the frame.

  • Page 46: Splitting The Cases

    INSPECTION NOTE: Inspect the cylinder head for deposits and abrasions. 1. If there are deposits they should be removed a. Black oily deposits (indicating a rich mixture or improper oil type/quantity) can be removed with solvent b. Crusty deposits (indicating dirt ingestion) can be removed with solvent and may require some scraping.

  • Page 47: Engine Assembly

    CAUTION: Take caution when handling the crankshaft. It is the main power transfer to the rest of the engine. If it is out of alignment, it will cause premature failure of your bearings which can lead to serious damage to the cylinder as well as the rest of the engine.
  • Page 48 Figure 28 9. Torque to 12 Nm (105 in-lb) in the pattern shown in figure 28. 10. Trim away any excess gasket material if necessary. NOTE: Check engine mount holes for excess material that may cause problems in engine installation. 11.

  • Page 49: Clutch

    NOTE: A light application of silicone grease can help hold the O-rings into position during assembly. Install O-RINGs as shown in figure 29. 17. Install the cylinder head. 18. Install the washers (with flat side down) and nuts. Torque to 105 in-lb (12 19.

  • Page 50: Clutch Washer Stackups

    CLUTCH REMOVAL: 1. Drain the engine transmission oil and remove the clutch cover. 2. Remove the clutch nut (not left hand thread) on the end of the crankshaft with the clutch nut removal tool. 3. Attach the Universal Puller. There are three 6mm clutch puller holes located on the ends of the center hub.
  • Page 51 Figure 32 Some configuration of clutch spring stack. Each ‘spring’ stack contains multiple springs (Belleville washers) - arranged into three, four, or five ‘flying saucers’, or turned away against the flat washer(s). Shown is the 4 ½ stack.. Stack Total Flying Saucers Turned Away Std.
  • Page 52 CAUTION: It is easy to prematurely damage the clutch and other engine components with improper clutch adjustment. If you are unsure of how to adjust the clutch, by even the slightest, contact the Cobra Technical Support Group before making adjustments. Clutch shoe wear: •...
  • Page 53 Figure 33, Clutch Assembly Drawing CLUTCH ASSEMBLY: 1. After cleaning or replacing the spring washers, reassemble the stack up of washers. CAUTION: It is important to reassemble the washer stack to that which is recommended or to your own specialized stack. CAUTION: It is also important that all three shoes are stacked the same.

  • Page 54: Ignition

    6. Put the clutch back in. 7. Apply high strength thread locking agent to the threads and install the nut and torque to 35 ft-lb (47Nm) with the special socket (see figure 33). CAUTION: Use high strength (red) thread locker on the threads of the clutch nut. If you are using an impact socket, just zap it lightly with an air wrench to tighten it because there are only about 4 threads inside the nut and they can be easily stripped.
  • Page 55 3. Improper spark plug heat range. Never run a hotter plug than the specified spark plug. 4. Clutch slippage. See “CLUTCH” section for causes of slippage. CAUTION: • 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.

  • Page 56: Cooling System

    0.040” before Figure 26, Lining up the line on the rotor Figure 27, Using a dial indicator to measure piston with the line on the stator. height for setting ignition timing. ROTOR INSTALLATION: 1. Torque the nut on the rotor to 40 ft-lb (54 Nm) with high strength (red) thread locking agent.
  • Page 57 Figure 28 To remove radiator cap: 2. Turn the cap counter clockwise to the first stop and wait there for a few seconds. 3. Push the cap down and turn it further in the same direction and remove the cap. NOTE: Inspect the old coolant for visual evidence of corrosion and abnormal smell.
  • Page 58 Figure 29 9. Heat engine case around area of impeller lightly with a small propane torch. Using a 3/8” diameter x 8” long steel rod, tap impeller assembly out of engine as shown in figure 30. Figure 30 CAUTION: Too much heat can be detrimental to the engine cases. 10.
  • Page 59 CAUTION: Clean all threads and use blue (medium strength) thread locker on the belt retainer screw. NOTE: Apply Ultra black Hi-Temp RTV silicon or Teflon pipe sealant to the tapered pipe threads of the coolant fitting before assembly. NOTE: Refill the coolant system with Liquid Performance Propylene Glycol based Mini Coolant / Antifreeze.

  • Page 60: Fuel & Air System

    Fuel & Air System Carburetor: Tools recommended for Carburetor carburetor service: • Small flat head screwdriver REF. # PART # DESCRIPTION RCCM0001 COMPLETE CARBURETOR 14MM • WD-40 RCMU0305 CARB SLIDE • 8mm socket RCMU0601 NEEDLE RCMU00 ATOMIZER AU 2.62 RCMU0092 MAIN JET RCMU0055 PILOT JET...
  • Page 61 Your Cobra is equipped with an adjustable carburetor. Some fine-tuning may be needed according to weather condition and altitude. Proper jetting is very important for engine performance and engine life. Serious damage to the engine can occur if not properly adjusted. IDLE ADJUSTMENT: On the left side of the carburetor, there are two adjustment screws.
  • Page 62 have water or dirt in the carburetor bowl. Use automotive carburetor cleaner or WD-40 to clean the carburetor inside and out. STOCK CARBURETOR SETTINGS The stock carburetor settings from the factory are: • 55 pilot jet • 92 main jet Cleaning the carburetor: Clean the carburetor in a well-ventilated area, and take care that there is no spark or flame anywhere near the working area;...

  • Page 63: Exhaust

    Take the reed cage out and hold it up to the light and look in through the cage. If you see light between the reed pedals and the frame, then replace the reeds. If you do not see light, then the reeds should be ok. (See figure 35) Figure 35 The presence of light indicates that the reeds should be replaced, or possibly turned over.

  • Page 64: Wheels & Tires

    Wheels & Tires Rear wheel pullers Disassembly: 1. Remove axle, back wheel assembly. 2. Pull the rear wheel pullers out of the back of the swing arm. Figure 36 Rear wheel alignment: Either • Accurately measure the distance from the swingarm pivot to the axle center on each side or •...
  • Page 65 1.3. Fork height 1.3.1. Rise in clamps for quicker turning. 1.3.2. Lower in clamps for improved straight line stability. 2. Rear shock 2.1. Shock spring (optional spring) 2.1.1. Stiffer spring – stiffer throughout the travel. 2.1.2. Less stiff spring – less stiff throughout the travel. 2.2.

  • Page 66: Rear Shock

    Proactive Suspension Adjustments Once you have the suspension adjusted for decent overall feel, you can make proactive adjustments when faced with different racing conditions. Situation Actions Sand track Lower the rear end (increase race sag). Sand track Stiffer compression and rebound damping. Long fast track Lower the forks in the clamps by 3 mm.

  • Page 67: Gearing

    Gearing For a bike with a centrifugal clutch, it’s better to be geared too low than too high. What happens with improper gearing? • Poor performance • Not enough top end speed • No snap • Over heat clutch • Premature failure of engine seals, bearings, &...
  • Page 68 Rear Front Sprocket Sprocket Gear Ratio 2.20 2.27 2.33 2.36 2.40 2.43 2.47 2.50 2.53 2.54 2.57 2.60 2.62 2.64 2.67 2.69 stock 2.71 2.73 2.77 2.79 2.80 2.85 2.86 2.92 2.93 3.00 3.00 3.08 3.15 3.23 Ratio Write © Cobra R&D 2004...

  • Page 69: Carburetion

    Carburetion Although your Cobra is sent from the factory with the carburetor jetted for optimal performance, you may find it necessary to adjustment your particular jetting due to current weather conditions, altitude, fuel variations, and/or engine modifications. CAUTION: Proper jetting is very important for engine performance and engine life. Symptoms of improper jetting are listed below.
  • Page 70 NOTE: • Before making any carburetor jetting changes verify that: o You are using the proper fuel and oil o The fuel is fresh and uncontaminated o The oil and fuel have been mixed in the proper ratio o The carburetor is clean (no plugged jets) o The air filter is properly clean and oiled o The float height is within proper specification (proper measuring technique is described later in this section)

  • Page 71: Troubleshooting

    TOP END JETTING: Adjust for clean full throttle acceleration Jet your top end (main jet) based on the acceleration of your Cobra Motorcycle on the longest straight at the track. Observe any of the lean or rich symptoms (spark plug appearance and bike performance) listed above and change your jetting accordingly.
  • Page 72 4) Engine cuts out at high RPMs a) Stator bad b) Carburetor diffuser plate upside down (install like a skirt) c) Plugged fuel petcock d) Silencer core tube broken 5) Engine won’t start a) Fuel None in tank ii) Is sour or bad b) Carburetor is dirty c) Ignition Spark plug fouled...

  • Page 73: Index

    Index Air Filter Maintenance ....14 Forks Airbox Parts ..........28 Parts.......... 18 Frame Parts ........30 Bars and Controls ......19 Frictional Drive ......17 Base Gasket Selection....41 Front Brake Break-In .......... 8 Parts ..........33 Carburetor Front Forks Service ........59 Service........65 Specifications ......
  • Page 74 Optional Components ..... 7 Rear Wheel Parts Parts ..........37 Airbox and Filter ......18 Pullers........63 Bars and Controls...... 19 Reeds..........61 Bottom End & Transmission ..23 Shock ..........65 Carburetor ......... 20 Parts ..........38 Clutch & Kick Starter ....24 Service........70 Coolant System ......

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