Cobra Moto CX50 Owner's Manual
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Cobra Moto CX50 Owner's Manual

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  • Page 2 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 Moto, LLC 240 Uran Street Hillsdale, Michigan 49242...
  • 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 ....................4 Specifications - General ..................4 Optional Suspension Components ..............5 Specifications - Torque Values ................5 Break-In Procedure ................... 6 Starting Procedure .................... 7 Maintenance ......................8 Tips ........................8 Schedule ......................9 Replacing Transmission / Clutch Lubricant .............
  • Page 5 Parts – Plastic & Seat ..................35 Parts – Rear Brake ..................36 Parts – Rear Wheel ..................37 Parts – Shock ....................38 Parts – Shock - Inside ..................39 Parts – Swingarm Assembly ................40 Service ........................ 41 Engine Service ....................

  • Page 6: General Information

    General Information Specifications - General Items CX50 JR Dimensions 35.75” (908mm) Wheelbase 10” (254mm) Wheel size 23.9” (607 mm) Seat height Engine Type 2-stroke, single cylinder, reed valve Cooling system Liquid-cooled Coolant 50/50 antifreeze-coolant / distilled water Displacement 49.8 cc Bore and stroke 39 mm x 41.7 mm...

  • Page 7: Optional Suspension Components

    Optional Suspension Components Weight of Rider (lb) Fork Spring Shock Spring KCCJ3218 Less than 38 (light) SCMUOH04 (275 lb/in) red (18 lb/in, 3.15 N/mm) KCCJ3221 SCMUOH05 (285 lb/in) 38 – 45 (std) (21 lb/in, 3.70 N/mm) yellow KCCJ3225 SCMUOH06 (295 lb/in) 46 to 55 (stiff) (25 lb/in, 4.40 N/mm) white...

  • Page 8: 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. Cobra recommends Bel-Ray H1-R premix oil with high octane pump gas mixed at 40:1 (150 ml oil to 2 gallons of gas).

  • Page 9: Starting Procedure

    Starting Procedure Before starting the machine inspect the following: Tire pressure Chain tension Coolant level Proper wear on chain rollers and sliders Handlebar tightness Throttle assembly movement/cable adjustment Air Filter Check for loose nuts and bolts Turn the fuel on by rotating the fuel petcock knob to the vertically downward position (reserve position is horizontally forward) NOTE: For best results from your Cobra Motorcycle use only the recommended fuel.

  • Page 10: Maintenance

    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). Example, CMxxxx7xxx is a 2007 MY CX50 JR. 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 11: Schedule

    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.

  • Page 12: Replacing Transmission / Clutch Lubricant

    Replacing Transmission / Clutch Lubricant Tools needed: 5mm allen wrench Minimum of 235 ml (8 oz) Cobra Venom 3 Shoe Clutch Milk (Part #MCMUGF32). Procedure: 1. Begin this procedure with a bike that has been ridden more than 5 minutes but less than 10 minutes.

  • Page 13: 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. A properly adjusted chain will have 50mm (13/8”) free movement behind the chain block with no load on the bike. (figure 2) Figure 2 Sit on the bike and verify that the chain has a...
  • Page 14 CAUTION: Use only DOT 4 brake fluid Setting rear brake pedal position (see figure 2b): 1. Loosen the lock nut (10mm wrench). 2. Adjust the brake lever stop (10mm wrench) so that the lever is comfortably reachable in both: a. Standing riding position, and Figure 2b b.

  • Page 15: Brake Bleeding Procedure

    Brake Bleeding Procedure Tools Required: Front: T10 Torx bit/driver, Cobra bleed kit (BCKG0031) Rear: 3mm hex key (Allen wrench, T10 Torx bit/driver, Cobra bleed kit(BCKG0031) Procedure: Remove the brake fluid reservoir cover. Fill the syringe half full with brake fluid. Remove the brake caliper bleed screw.

  • Page 16: Air Filter Cleaning

    Air Filter Cleaning Tools recommended for air filter maintenance: #2 Phillips head screwdriver 4 mm Allen wrench Foam filter oil Procedure 1. Removed the seat with a 4 mm Allen wrench. 2. Remove the filter/air inlet boot from the back of the carburetor with a Phillips screwdriver 3.

  • Page 17: Fork Oil Replacement

    Fork Maintenance Cobra strongly recommends that a professional service technician conduct all internal maintenance other than changing springs and oil. This will help to ensure safe and consistent operation. For routine maintenance, the chart below provides suggested service intervals for common procedures: Each Ride 10 hours 20 hours...

  • Page 18: Cobra Frictional Drive (V3 Cfd)

    Disassembly procedure 1. Remove the front wheel (19 mm wrench). 2. Remove the brake caliper from the fork leg (4 mm hex key). 3. Loosen the fork caps (32mm fork cap tool). 4. Remove the fork legs from the triple clamps (5 mm hex key). 5.
  • Page 19 The slip torque value should be above 60 ft-lb (81 Nm) measured at the sprocket. To properly measure the minimum torque at which the CFD (Cobra Frictional Drive) slips 1. Access the slip clutch by draining the oil and removing the cover exposing the CFD.

  • Page 20: Parts

    Parts Parts – Airbox and Inlet System Airbox and Inlet System REF # PART # DESCRIPTION GASKET – REED TO CYLINDER ZCCS0001 ECMU0246 REED CAGE ASSEMBLY WITH REEDS VFORCE RCCS0002 INLET MANIFOLD HCWF0601 6mm FLAT WASHER HCBC0603 M6X30mm SOCKET HEAD CAP SCREW HOSE CLAMP –...

  • Page 21: Parts - Bars And Controls

    Parts – Bars and Controls Bars and Controls REF # PART # DESCRIPTION HANDLEBAR - ALUMINUM GRIPS (SET OF TWO) – SCOTT WAFFLE TCMU0008 FCMU0066 THROTTLE ASSEMBLY FCPW0004 CABLE COVER FCMU0021 THROTTLE COVER FCMU0019 THROTTLE CABLE BAKG0003 BRAKE ASSEMBLY FRONT FCMU0033 KILL SWITCH ASSEMBLY M8X30mm SOCKET HEAD CAP SCREW (4) REQ’D...

  • Page 22: Parts - Carburetor

    Parts - Carburetor Carburetor REF. # PART # DESCRIPTION RCCM0001 COMPLETE CARBURETOR 14MM RCMU0305 SLIDE - #40 RCMU0601 NEEDLE - W7 RCMU0024 ATOMIZER AU2.62 RCMU00xx MAIN JET, xx denotes size RCMU00xx PILOT JET, xx denotes size RCMU0301 FLOAT RCMU0102 RUBBER CABLE CAP SEAL RCMU0003 CABLE ADJUSTOR RCMU0006...

  • Page 23: Parts - Coolant System

    Parts – Coolant System Coolant System REF # PART # DESCRIPTION FCCJ0004 RADIATOR WITH CAP MCMUHO02 RADIATOR HOSE LEFT MCMUCL07 HOSE CLAMP MOUNTING BRACKET – RADIATOR BOTTOM EACJ0001 HCBC0608 M6X55mm SOCKET HEAD CAP SCREW HCNL0601 M6 LOCK NUT GROMMET – RADIATOR MOUNTING MCKGGR00 MCCMHO01 RADIATOR HOSE RIGHT...

  • Page 24: Parts - Electrical System

    Parts – Electrical System Electrical System REF # PART # DESCRIPTION ICCJ0001 COIL W/SPARK PLUG CAP ECMU0010C SPARK PLUG, AUTOLITE COPPERLITE ECMU0010I SPARK PLUG, AUTOLITE IRIDIUM FCMU0033 KILL SWITCH ASSEMBLY M5X16mm HEX HEAD SCREW (2 REQ’D) HCBH0502 5mm WASHER (2 REQ’D) HCWF0501 5mm WASHER SPECIAL (2 REQ’D) HCWP0002...

  • Page 25: Parts - Engine - Bottom End And Transmission

    Parts – Engine – Bottom End and Transmission Engine Bottom End and Transmission REF # PART # DESCRIPTION 1 & 2 EKCS0003 ENGINE CASE SET W/B&S 50 2012 ZCCS0005 GASKET, CRANKCASE CENTER M6X40mm SOCKET HEAD CAP SCREW (6 REQ’D) HCBC0605 M6X55mm SOCKET HEAD CAP SCREW (1 REQ’D) HCBC0608 M6X45mm SOCKET HEAD CAP SCREW (2 REQ’D)

  • Page 26: Parts - Engine Clutch And Kicker

    Parts – Engine Clutch and Kicker Engine – Clutch and Kick Starter REF # PART # DESCRIPTION CAMU0006 CLUTCH COMPLETE CAMU0013 CLUTCH SHOES (SET OF 3) WITH BOLT & WASHERS CCMU0005 CLUTCH ARBOR CAMU0010 SPRINGS, WASHERS & BOLTS (SET OF 3) CLUTCH BOLT (3 REQ’D) HCBS0004 ECMU0018...
  • Page 27 Parts – Engine – Water Pump Engine – Water Pump REF # PART # DESCRIPTION EKMU0011 WATER PUMP KIT WITH IMPELLER ECKG0142 SHAFT, WATER PUMP ECKG0072 BEARING, WATER PUMP ECKG0074 SEAL, WATER PUMP SHAFT ECKG0073 IMPELLER, WATER PUMP (ALUMINUM) HCBC1512 M5X12mm SOCKET HEAD CAP SCREW (STAINLESS) BEARING –WATER PUMP BIG ECMU0167...

  • Page 28: Parts - Engine - Top End

    Parts – Engine – Top End Engine – Top End REF # PART # DESCRIPTION ECCJ0001 CYLINDER (INCLUDES PISTON, RINGS, PIN & CLIPS) ZCMU0011 BASE GASKET (0.25mm) THICK ZCMU0703 BASE GASKET (0.30mm) THICK ZCKG0501 BASE GASKET (0.40mm) THICK (STANDARD) ZCMU0705 BASE GASKET (0.50mm) THICK ZCMU0706 BASE GASKET (0.60mm) THICK...

  • Page 29: Parts - Exhaust System

    Parts – Exhaust System Exhaust System REF # PART # DESCRIPTION XCCJ2009 CX50JR EXHAUST PIPE HEADER PIPE O-RINGS (2 REQ’D) ZCMOTE11 XCMU0005 EXHAUST SPRING - SHORT MCMUGR02 GROMMET KIT XCMU0028 PIPE / SILENCER SEAL XCMU0032 SILENCER MOUNTING GROMMET (2 REQ’D) MCMUGR03 SPACER (2 REQ’D) TCKG0001...

  • Page 30: Parts - Forks & Triple Clamps

    Parts – Forks & Triple Clamps Front Forks and Triple Clamps REF # PART # DESCRIPTION KACJ0001 FORK ASSEMBLY FORK LEGS ONLY KCMU0011 FORK GUARD SET WASHER FORK GUARD (4 REQ’D) TCC60019 M6X16mm, SOCKET HEAD CAP SCREW (4 REQ’D) HCBC0601 BCC60015 BRAKELINE CLAMP M6X12mm, SOCKET HEAD CAP SCREW (2 REQ’D)

  • Page 31: Parts - Forks - Leg Assembly - Brake Side

    Parts – Forks – Leg Assembly – Brake Side REF # PART # DESCRIPTION HCBC0408 4 X 8 SHCS CLEAR ZINC ZCKG0001 GASKET, BLEED SCREW FORK KCCS0004C FORK CAP - CONVENTIONAL 32MM USD ZCMUOR18 O-RING PV SOLENOID - CX65 KCCS0036 FORK - SPRING WEAR PLATE 32MM KCCS0005 FORK - OUTER TUBE 32MM...

  • Page 32: Parts - Forks - Leg Assembly - Non-Brake Side

    Parts – Forks – Leg Assembly – Non-Brake Side REF # PART # DESCRIPTION HCBC0408 4 X 8 SHCS CLEAR ZINC ZCKG0001 GASKET, BLEED SCREW FORK KCCS0004S FORK CAP - CONVENTIONAL 32MM USD ZCMUOR18 O-RING PV SOLENOID - CX65 KCCS0036 FORK - SPRING WEAR PLATE 32MM KCCS0005 FORK - OUTER TUBE 32MM...

  • Page 33: Parts - Frame - Mounting Hardware I

    Parts – Frame – Mounting Hardware I Frame – Engine, Swingarm, Tank, and Pipe Mounts REF # PART # DESCRIPTION WCMU0016 SWINGARM BOLT HCNL1201 M12 SWINGARM LOCK NUT HCBH0880 M8X80mm SOCKET HEAD CAP SCREW HCNL0801 M8 LOCKNUT MCMUGR02 GROMMET KIT PIPE & SPACER HCBF0635 M6X35mm FLANGE HEAD BOLT HCHA0003...

  • Page 34: Parts - Frame - Mounting Hardware Ii

    Parts – Frame – Mounting Hardware II Frame – Seat, Fender, Right Side Panel, Radiator & Shock Mounts REF # PART # DESCRIPTION FACJ2012 FRAME CX50 JR HCBF1040 M10X40mm FLANGE HEAD BOLT MOUNTING BRACKET – RADIATOR BOTTOM ECCJ0001 HCBC0608 M6X55mm SOCKET HEAD CAP SCREW...

  • Page 35: Parts - Front Brakes

    Parts – Front Brakes Front Brakes REF # PART # DESCRIPTION BAKG0003 FRONT BRAKE ASSEMBLY HOSE – BRAKE FRONT BCKG0030 BCKG0023 ALLOY BRAKE LEVER BCKG0024 BRAKE PERCH & MASTER CYLINDER ASSY W/ LEVER CALIPER – FRONT BCKG0029 KIT BRAKE PADS, WITH “E” CLIP BKKG0001 BCMU0503 BRAKE ROTOR...

  • Page 36: Parts - Front Wheel

    Parts – Front Wheel Front Wheel REF # PART # DESCRIPTION WACJ0001 WHEEL WITH BEARINGS SPOKE STYLE WCMU0016 FRONT AXLE M5X12mm SOCKET HEAD CAP SCREW (6 REQ’D) HCBC0501 BRAKE ROTOR – FRONT BCMU0503 WCMU0101 WHEEL SPACER LEFT (SHORT) BEARING – WHEEL (2 REQ’D) WCMU0120 SPACER –...

  • Page 37: Parts - Plastic & Seat

    Parts – Plastic & Seat Plastic and Seat REF # PART # DESCRIPTION TCHA0107Y FRONT FENDER FRONT FENDER x – DENOTES COLOR BLK, WHT, YEL, FLO TCHA0107x FENDER BOLT, M6X16mm FLANGE HEAD (4 REQ’D) HCBF0616 NUMBER PLATE – FRONT TCC60002W FRONT PLATE x –...

  • Page 38: Parts - Rear Brake

    Parts – Rear Brake Rear Brake System REF # PART # DESCRIPTION BRAKE SYSTEM – REAR (M/C-LINE-CALIPER) BAKG0002 BCMU0027 BRAKE PIVOT BOLT SEAL – BRAKE PEDAL (2 REQ’D) BCMU0501 BCMU0023 BRAKE PEDAL BCMU0023T TOE PIECE HCBC0501 M5X 12mm SOCKET HEAD CAP SCREW BCMUSP02 BRAKE RETURN SPRING HCBC0601...

  • Page 39: Parts - Rear Wheel

    Parts – Rear Wheel Rear Wheel REF # PART # DESCRIPTION WAKG2007R REAR WHEEL W/BEARINGS TIRE – REAR 10X2.75” DUNLOP MX51 WCMU1075D WCMUTU10 TUBE, 10" PCMU0001 MASTER LINK 420 PCMU0100 CHAIN 420 X 100 PCMU0138 38T SPROCKET (STANDARD) SPROCKET xx DENOTES TEETH – RANGE OF TEETH (34-45) PCMU01xx M7X30mm HEX HEAD BOLT (4 REQ’D) HCBH0702...

  • Page 40: Parts - Shock

    Parts – Shock Rear Shock REF# PART # DESCRIPTION SACJ2012 SHOCK ABSORBER SHOCK – BEARING SPERICAL SHOCK MOUNT – (2REQ’D) SCMU0043 O-RING – SHOCK – BUSHING (4 REQ’D) SCMU0039 SHOCK – MOUNT BUSHING (4 REQ’D) SCMU0042 SHOCK – WHITE NYLON TIP SET SCREW M6-1.0 SCMU0058 SHOCK –...

  • Page 41: Parts - Shock - Inside

    Parts – Shock - Inside Rear Shock REF# PART # DESCRIPTION SCMU0037 O-RING LOW SPEED COMP ADJUSTER SCMU0038 O-RING HIGH SPEED COMP ADJUSTER SCMU0036 O-RING COMP ADJUSTER CAP SCC60007 O-RING COMPRESSION ADJUSTER SCMU0051 O-RING - IFP SCMU0052 IFP SEAL BAND SCMU0033 O-RING SHOCK BASE SCMU0050...

  • Page 42: Parts - Swingarm Assembly

    Parts – Swingarm Assembly Swingarm REF # PART # DESCRIPTION GACJ2011 SWINGARM SWINGARM BUSHING (SINGLE PIECE) (4 REQ’D) GCMU0001 SPACER - PIVOT TUBE (2REQ’D) GCCJ0001 GCMU0017 CHAIN GUARD HCFH0512 M5X12mm FLAT HEAD SCREW HCWF0501 5mm FLAT WASHER HCNL0501 M5 LOCK NUT M6X20mm FLANGE HEAD BOLT (2 REQ’D) HCBF0620 CHAIN GUIDE –...

  • Page 43: 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 44: Base Gasket Selection

    3. Hold the throttle 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 17mm wrench 1mm flexible solder material measurement calipers When rebuilding the ‘top end’ of your Cobra motorcycle, care must be taken to ensure the proper squish clearance.
  • Page 45 If top end parts are changed during the course of the maintenance, 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 46: Engine Removal

    Engine Removal To service the bottom end/transmission, the engine must be removed from the frame. Tools required 10, 11, 13, 22 mm wrench 8, 10, 14, 17 & 19 mm sockets 3, 4 & 5 mm Allen wrench 7 mm nut driver, flat or Phillip, screwdriver for hose clamps Spring remover Flywheel / clutch puller (#MCMUTL68) Clutch nut removal tool (#ECMU0078)

  • Page 47: Top End Disassembly Procedure

    6. Remove the left hand thread nut holding the CFD to the transmission input shaft using the CFD gear stop (#EAMU0004) and a 19mm socket. 7. Remove the clutch nut / starter gear that holds on the clutch using the clutch nut removal tool (#ECMU0078).

  • Page 48: Splitting The Cases

    INSPECTION NOTE: Inspect the piston for abrasions and deposits on the top and sides and clean or replace as necessary. INSPECTION NOTE: Piston ring end gap should be between 0.006” (0.16 mm) and 0.020” (0.5 mm) Splitting the Cases 1. Remove the fasteners holding the two halves of the crankcase together. 2.
  • Page 49 9. Trim away any excess gasket material if necessary. NOTE: Check engine mount holes for excess material that may cause problems in engine installation. 10. Install the piston with new wrist pin bearing and, pin and clips. CAUTION: Be sure to install the piston such that the arrow on the top piston surface points to the exhaust (front of bike/engine) and put assembly lube on the connecting rod bearing.

  • Page 50: Clutch

    Ignition portion of this manual. 22. Install the water pump outlet pipe (apply Hi-Temp RTV silicon gasket maker to the threads before assembly) before installing the clutch and rotate to a vertical position with the engine resting on bench 23. Install the CFD. 24.

  • Page 51: Clutch Washer Stackups

    Figure 30 Figure 31 Clutch puller installation CAUTION: Do not use a jaw type puller or use the 6mm tapped holes as jackscrews or you are likely damage the clutch or drum. CAUTION: It is possible to cause damage to the piston when using the piston stop. Care must be used when removing and installing the clutch arbor and using the piston stop.
  • Page 52 CLUTCH ASSEMBLY REFERENCE DRAWING REF # PART # DESCRIPTION CAMU0013 Set of three shoes, springs, bolts, flat washers & nuts CAMU0010 Set Of three springs, washers, bolts & nuts CAMU0006 Complete assembled clutch Not Shown (Arbor, shoes and washer stacks) Figure 32 Some configuration of clutch spring stack.
  • Page 53 Use the table above to order adjustment washers. Replace the stock washer with the proper combination of adjustment washers that delivers the desired clutch hit. 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, contact the Cobra Technical Support Group before making adjustments.

  • Page 54: Ignition

    2. Clean the threads of the stack bolt and the clutch with brake cleaner removing all old thread locking material. 3. Assemble the stacks and shoes on the arbor using high strength thread lock material to the stack bolt and tighten to 12 ft-lb (16 N-m). CAUTION: Avoid allowing excess thread lock material to contact the spring washers and the clutch or the clutch is likely to malfunction.
  • Page 55 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. The heat transfers through the cases and can damage the stator as it cools off because of lack of airflow around the stator.

  • Page 56: Cooling System

    6. Set the dial indicator to zero 7. Turn the crankshaft clockwise until the dial indicator reaches 0.040” (1.0mm) from top dead center. 8. At this position the line on the rotor should align with the center of the stator coil at 5 o’clock position on stator frame.
  • Page 57 Tools recommended for impeller service: Flat head screwdriver 13mm- hex wrench 3mm hex key 4mm hex key 5mm hex key 8mm hex key Water Pump Installation tool MCMUTL09, 2010 and newer JR & King MCMUTL08, 2009 and older JR models Slide hammer with fitting to thread into threads on end of shaft (M5x1.0) single and double hook ends for removing plastic impeller...
  • Page 58 9. Prepare for assembly by installing the water pump assembly into the assembly tool and align the tool with engine case making sure alignment pin is in proper hole. CAUTION: Damage may occur if one attempts to install the water pump and the device is not orientated correctly.

  • Page 59: Fuel & Air System

    13. Reinstall the pulley, belt and fan cover using a 3mm hex key to stop the rotation of the water pump assembly while tightening with medium strength thread lock to 10 ft-lb (14Nm). 14. Reinstall the cover NOTE: Refill the coolant system with 50/50 antifreeze-coolant / distilled water. CAUTION: Do not mix Propylene Glycol based coolant / antifreeze solutions with Ethylene Glycol based coolant / antifreeze solutions.
  • Page 60 Indications that the engine is running too lean are: Engine cutting out on top end. Engine overheating and ultimately seizure. White spark plug CAUTION: It is much safer to operate the engine slightly rich as opposed to slightly lean. This is because an overly rich engine will just run poorly while an overly lean engine will seize, potentially causing an expensive top end rebuild and a DNF.

  • Page 61: Reeds

    Reeds The reeds must lay flat on the reed cage. If the reed tips aren’t lying flat, replace them immediately. The reeds must have a tight seal on the reed cage. If the reed is damaged in any way, replace it. This means cracks, chips, and ruptures.

  • Page 62: Rear Wheel Pullers

    Rear wheel pullers Disassembly: 1. Remove axle, and back wheel assembly. 2. Pull the rear wheel pullers out of the back of the swing arm. Figure 47 Rear wheel alignment: Either Accurately measure the distance from the swingarm pivot to the axle center on each side or From the rear of the bike, sight up through both sprockets to ensure that the chain is running in a straight line (no bend in between or jog at either...
  • Page 63 Front Forks Tools recommended for front fork service: Flat head screwdriver Hammer Pick Seal driver MCMUTL02 9/16” (loose 14 mm) wrench 25mm wrench or socket 2.5 wt fork oil FORK DISASSEMBLY PROCEDURES: o Using the 25mm wrench, remove the fork cap. o Drain the fork oil into a suitable container.

  • Page 64: Rear Shock

    See Optional Components section of this manual for details on these and other optional components for your Cobra Motorcycle. Rear Shock The rear shock is fully serviceable but it is recommended that only trained professionals should service your shock. Contact Cobra for questions and service of your CX50 SR shock.

  • Page 65: Tuning

    Tuning Clutch There are performance characteristics to observe and things to measure. 1) Performance characteristics to observe a) Clutch coming in too late i) Engine rev’s to a high RPM before moving the motorcycle ii) Clutch never fully engages on a reasonable straight stretch iii) Basket turns blue in short amount of time b) Clutch coming in too early i) Motorcycle moves too soon when accelerating off idle...
  • Page 66 1. Clutch spring stack to tall Wrong configuration Too thick a flat shim in the stack 2. Spring rate too high (wrong configuration with proper stack height) 3. Clutch arbor shoulder bolt is too short 4. Clutch shoe material has worn too thin 5.
  • Page 67 Effective length of the shoulder on the clutch arbor bolt (see Figure C1). Nominal is 16.00mm (0.630”). As this decreases, the spring stack needs to decrease equally. This can change due to the shoulder bolt ‘setting’ into the arbor (see C2) Figure C1 Figure C2 If your effective shoulder length is off, or your shoes are worn, adjust the height...

  • Page 68: Gearing

    Gearing For a bike with a centrifugal clutch, it’s better to be geared too low than too high. Condition Gear Taller Gear Lower What happens with improper gearing? Sand Poor performance Hills Not enough top end speed Hard Pack No snap Throttle Blipper (novice)* Over heat clutch Premature failure of...

  • Page 69: Suspension

    Suspension Adjustment 1. Front forks 1.1. Fork oil 1.1.1. Oil type Heavier weight oil – more damping – slower responding 1.1.1.1. Lighter weight oil – less damping – quicker responding 1.1.1.2. 1.1.2. Oil quantity / level Greater quantity / higher level – greater bottoming 1.1.2.1.
  • Page 70 Front Fork Operation The front suspension on the CX50SR works under the principals of hydraulic damping, and it features full adjustability to help tune the fork to meet each rider’s needs. The CARD fork contains MXT ‘Smart Leg’ technology that provides very progressive operation;...

  • Page 71: Rear Shock

    it counter-clockwise will decrease it. This is illustrated by the “HARD” and “SOFT” in the figure at the right. The Smart Leg cap is labeled “Speed Sensitive Bottoming Control”, and this adjuster provides a range of control over how progressive the fork feels. Turning the screw clockwise increases the fork’s resistance to bottoming, while turning the screw counter-clockwise decreases it.

  • Page 72: Carburetion

    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 73 CAUTION: Proper jetting is very important for engine performance and engine life. Symptoms of improper jetting are listed below. Symptoms of incorrect oil or oil / fuel ratio o Poor acceleration o Misfire at low engine speeds o Excessive smoke o Spark plug fouling o Excessive black oil dripping from exhaust system Symptoms of too rich a fuel mixture...
  • Page 74 NOTE: Perform all jetting changes on a motorcycle that has been warmed up to proper operating temperature. The carburetor on your Cobra motorcycle is quite adjustable. Figure 59 shows its range of adjustment and in particular what adjustable component affects what range of operation (specifically throttle position).

  • Page 75: Troubleshooting

    Troubleshooting 1) Engine not behaving properly a) Carburetor top is installed backwards (happens a lot) b) The carburetor slide indexing pin is missing c) Wrong spark plug installed (8339 Champion to be used on ’04 or later & no mods) d) Needle clip is on top of plastic not below e) Air leak –...
  • Page 76 Spark plug fouled ii) Wrong spark plug installed (8339 Champion to be used on ’04 or later & no mods) iii) Spark plug cap off iv) Engine Shut-off ‘kill’ switch is shorted v) Bad electrical ground vi) Stator winding damaged d) Exhaust is plugged 6) Overheating a) Bad stator...

  • Page 77: Index

    Index Air Filter Maintenance ....14 Frame Parts ........31 Airbox Frictional Drive ......16 Parts .......... 18 Front Brake Parts .......... 33 Bars and Controls ......19 Base Gasket Selection ....42 Front Wheel Parts ......34 Break-In .......... 6 Fuel System Carburetor Service ........
  • Page 78 Engine ........23 Parts ........38, 39 Exhaust ........27 Slip Clutch ........16 Spark Plug Forks ......... 28 Recommended ......4 Frame ........31 Specifications ........4 Front Brake ....... 33 torque values ....... 5 Front Wheel ....... 34 Starting ..........

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