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Pinned Honda CBR250RR MC22 Specifications

Discussion in 'Honda 250cc In-line 4's' started by kiffsta, Jul 12, 2014.

  1. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    My Bike:
    90 CBR250RR ,Suzuki T500, 2005 GSF1200 Bandit and a 1972 t250j

    mc22.jpg


    Configuration

    Liquid-cooled 4-stroke 16-valve DOHC in-line 4 cylinder

    Power
    Horsepower: 45 hp (33.6 kW) @ 15000 rpm
    Maximum Torque: 21.5 Nm (15.6 ft. lbs) @ 12000 rpm

    Performance
    Top Speed: ~180kph (113mph)
    0-100kph (0-60mph): ~5 Seconds

    Transmission
    6-speed Gear Ratios: 1st 2.733 2nd 2.000 3th 1.590 4th 1.333 5th 1.153 6th 1.035
    Primary Drive Ratio: 2.966
    Bore & Stroke 48.5 x 33.8

    Ignition
    Electronic

    Fuel Capacity
    13 Litres
    1.6 Litre reserve

    Battery
    Yuasa Yumicron YTLBX7

    Charging System
    12v

    Compression Ratio
    11.5:1

    Clutch
    Wet multiple plate coil springs

    Intake
    4 inline carbs

    Tires
    Front: 110/70-17
    Rear: 140/70-17

    Dimensions
    Overall - Length: 1975 mm (77.8 inches)
    Overall - Width: 675 mm (26.6 inches)
    Overall - Height: 1080 mm (42.5 inches)
    Seat Height: 725 mm (28.5 inches)
    Wheelbase 1345 mm (53 inches)
    Ground clearance 130 mm (5.1 inches)
    Fuel Capacity: 13 l (3.4 Gal)
    Dry Weight (without fluids): 142 kg (313.1 pounds)

    Brakes
    Front: dual 275 mm discs with 2-piston calipers Rear: single 220 mm disc with 1-piston calipers

    Honda CBR250RR Years of Manufacture

    1990-91: CBR250RR (L)
    The first of the 250RR series. The only remaining feature from the predecessor (CBR250R) was the MC14E engine, with slight modifications to the crankshaft and carburettor.

    1992-93: CBR250RR (N)
    The same as the L model except with new paint jobs.

    1994-96: CBR250RR
    The last models to be manufactured, and the only model containing the restricted 30kW engines.

    1997-99: CBR250RR (RII)
    Left over models from the 94-96 production.


    General

    Cylinder numbering (from left to right when sitting on bike) : 1 – 2 – 3 – 4
    Firing Order : 1 – 2 – 4 – 3
    Spark Plugs :
    Type : NGK CR9EH–9 or (CR9EHVX–9)
    Gap : 0.8 – 0.9 mm
    Top Speed : 180km/h (speed limited), unrestricted 200km/h (approx.)
    Max Power : (BHP = PS * 0.986) (kW = BHP * 0.7457)
    CBR250(F) : 45PS at 14,500rpm
    CBR250R(H+J+K) : 45PS at 15,000rpm
    CBR250RR(L+N) : 45PS at 15,000rpm
    CBR250RR® : 40PS at 14,500rpm
    Max Torque : (Lb/ft = kg/m * 7.233) (Nm = kg/m * 9.804)
    CBR250(F) : 2.5kg/m at 10,500rpm
    CBR250R(H+J+K) : 2.6kg/m at 10,500rpm
    CBR250RR(L+N) : 2.5kg/m at 12,000rpm
    CBR250RR® : 2.4kg/m at 11,500rpm

    Carburettor Type : Keihin 4 x CV
    Starter : Electric
    Clutch : Wet Multi–Plate
    Transmission : 6–speed Constant Mesh
    Final Drive : Chain
    Bore x Stroke : 48.5mm x 33.8mm
    Displacement : 249cm3

    Tyre Pressure (unless indicated on tyre sidewall);
    CBR250(F) + CBR250R(H);
    Front : 2.0kg/cm2
    Rear : 2.5kg/cm2
    CBR250R(J+K) + CBR250RR(L+N+R);
    Front : 2.25kg/cm2
    Rear : 2.5kg/cm2

    Tyres:
    CBR250(F+H);
    Front : 100/80–17 52H
    Rear : 130/70–17 62H
    CBR250R(J+K);
    Front : 100/80–17 52H
    Rear : 140/70–17 66H
    CBR250RR(L+N+R);
    Front : 110/70R17 54H
    Rear : 140/60R17 63H

    Suspension

    Front Suspension : Conventional Forks - 37mm Diameter (No Adjustments)
    Rear Suspension : Mono Shock (Preload only adjustments)


    Front Brake
    CBR250(F)+CBR250R(H):???mm Dual disc,2 piston Hydraulic callipers
    CBR250R(J+K) : ???mm Single disc, 2 piston Hydraulic callipers
    CBR250RR(L+N+R) : 275mm Dual disc, 2 piston Hydraulic callipers
    Rear Brake;
    CBR250(F) : 141mm Cable Drum Brake
    CBR250R(H+J+K) + CBR250RR(L+N+R) : 220mm Single disc, 1 piston
    Hydraulic calliper
    Dimensions : (Length x Width x Height)
    CBR250(F) : 2000x685x1120
    CBR250R(H) : 2000x680x1120mm
    CBR250R(J+K) : 2020x685x1075mm
    CBR250RR(L+N+R) : 1975x675x1080mm

    Wheel Base :
    CBR250(F) : 1370mm
    CBR250R(H) : 1365mm
    CBR250R(J+K) : 1365mm
    CBR250RR(L+N+R) : 1345mm

    Ground Clearance :
    CBR250R(F+H) : 140mm
    CBR250R(J+K) : 135mm
    CBR250RR(L+N+R) : 130mm

    Weight (Dry) :
    CBR250(F) : 153kg (77kg – Front, 76kg – Rear)
    CBR250R(H) : 155kg (78kg – Front, 77kg – Rear)
    CBR250R(J+K) : 154kg (77kg – Front, 77kg – Rear)
    CBR250RR(L+N) : 157kg (80kg – Front, 77kg – Rear)
    CBR250RR® : 158kg (81kg – Front, 77kg – Rear)


    Engine (Liq.–cooled,4–stroke,16–valve DOHC,inline 4 Cyl.)
    Engine Oil Type : API grade SE, SF or SG motorcycle oil
    Engine Oil Viscosity : SAE10W–40 or SAE20W–50
    Oil Capacity :
    Oil change : 2.2 litres
    Oil and Filter change : 2.4 litres
    Engine overhaul with new filter : 2.7 litres
    Oil Pressure : 4.0 – 5.0kg/cm2 at 6,000rpm, oil at 60oC
    Inlet Valve (1mm Lift);
    Opens (Before Top Dead Centre);
    CBR250(F) : 10Ъ BTDC
    CBR250R(H) : 18Ъ BTDC
    CBR250R(J+K) + CBR250RR(L+N) : 19Ъ BTDC
    CBR250RR® : 20Ъ BTDC
    Closes (After Bottom Dead Centre);
    CBR250(F) : 40Ъ ABDC
    CBR250R(H) : 34Ъ ABDC
    CBR250R(J+K) + CBR250RR(L+N) : 33Ъ ABDC
    CBR250RR® : 20Ъ ABDC

    Exhaust Valve (1mm Lift);
    Opens (Before Bottom Dead Centre);
    CBR250(F) : 30Ъ BBDC
    CBR250R(H+J+K) + CBR250RR(L+N) : 36Ъ BBDC
    CBR250RR® : 29Ъ BBDC
    Closes (After Top Dead Centre);
    CBR250(F) : 10Ъ ATDC
    CBR250R(H+J+K) + CBR250RR(L+N) : 11Ъ ATDC
    CBR250RR® : 3Ъ ATDC
    Cam Lobe Diameter;
    CBR250(F) + CBR250R(H) :
    IN : 29.15mm
    Service Limit : 29.00mm
    EX : 28.85mm
    Service Limit : 28.70mm
    CBR250R(J+K) :
    IN : 29.44 – 29.68mm
    Service Limit : 29.41mm
    EX : 28.96 – 29.20mm
    Service Limit : 28.85mm
    CBR250RR(L+N) :
    IN : 28.94 – 29.18mm
    Service Limit : 28.91mm
    EX : 28.51 – 28.75mm
    Service Limit : 28.48mm
    CBR250RR® :
    IN : 28.72 – 28.80mm
    Service Limit : 28.69mm
    EX : 28.51 – 28.75mm
    Service Limit : 28.48mm
    Cam Journal Diameter : 19.978 – 19.993mm
    Service Limit : 19.970mm
    Cam Journal Oil Clearance;
    Cylinders 1,2,4 : 0.015 – 0.057mm
    Service Limit : 0.06mm
    Cylinder 3 : 0.025 – 0.067mm
    Service Limit : 0.07mm
    Head INLET;
    Stem Diameter :
    CBR250(F) : 3.970 – 3.995mm
    Service limit – 3.965mm
    CBR250R(H) : 3.478 – 3.492mm
    Service limit – 3.473mm
    CBR250R(J+K) + CBR250RR(L+N+R) : 3.481 – 3.495mm
    Service limit – 3.47mm
    Guide Bore Diameter :
    CBR250(F) : 4.000 – 4.012mm
    Service limit – 4.065mm
    CBR250R(H+J+K) + CBR250RR(L+N+R) : 3.500 – 3.512mm
    Service limit – 3.565mm
    Stem to Guide Clearance :
    CBR250(F) : 0.005 – 0.042mm
    Service limit – 0.1mm
    CBR250R(H) : 0.008 – 0.034mm
    Service limit – 0.092mm
    CBR250R(J+K) + CBR250RR(L+N+R) : 0.005 – 0.042mm
    Service limit – 0.1mm
    Seat Width : 0.8mm
    Service limit – 1.3mm
    Head EXHAUST;
    Stem Diameter :
    CBR250(F) : 3.950 – 3.975mm
    Service limit – 3.935mm
    CBR250R(H+J+K) + CBR250RR(L+N+R) : 3.460 – 3.475mm
    Service limit – 3.445mm
    Guide Bore Diameter :
    CBR250(F) : 4.000 – 4.012mm
    Service limit – 4.065mm
    CBR250R(H+J+K) + CBR250RR(L+N+R) : 3.500 – 3.512mm
    Service limit – 3.565mm
    Stem to Guide Clearance :
    CBR250(F) : 0.005 – 0.050mm
    Service limit – 0.13mm
    CBR250R(H) : 0.025 – 0.052mm
    Service limit – 0.132mm
    CBR250R(J+K) : 0.005 – 0.050mm
    Service limit – 0.13mm
    CBR250RR(L+N+R) : 0.020 – 0.047mm
    Service limit – 0.13mm
    Seat Width : 1.0mm
    Service limit – 1.5mm
    Valve Spring Free Length (IN and EX) :
    CBR250(F) : 37.3mm
    Service limit – 36.3mm
    CBR250R(H) : 38.58mm
    Service limit – 37.6mm
    CBR250R(J+K) : 37.3mm
    Service limit – 36.3mm
    CBR250RR(L+N+R) : 37.65mm
    Service limit – 36.65mm
    Inlet Port Diameter :
    CBR250(F) : 28mm ???
    CBR250R(H) : 30mm ???
    CBR250R(J+K) : 32mm ???
    CBR250RR(L+N) : 30mm ???
    CBR250RR® : 25mm ???
    Valve Clearances (COLD Engine, i.e. leave engine overnight)
    Inlet valves : 0.16mm ± 0.03mm
    Exhaust valves : 0.23mm ± 0.03mm

    Cylinder Compression :
    CBR250(F) + CBR250R(H+J+K) : 11.0 to 1
    CBR250RR(L+N+R) : 11.5 to 1
    Cylinder Head : Warpage (max) – 0.10mm

    Bore to Piston Clearance : 0.01mm – 0.04mm
    Service Limit – 0.1mm

    Clutch
    Friction Plates : 7
    Plain Plates (Steelies) : 6
    Friction Plate Thickness : 2.6mm
    Plain Plate Warpage : 0.3mm
    Spring Free Height : 33.79mm

    Chain
    CBR250(F) + CBR250R(H) : 520 Pitch, 108 Links
    CBR250R(J+K) + CBR250RR(L+N+R) : 428 Pitch, 136 Links
    Gear Box;
    Primary Reduction Ratio : 2.966
    Ratios;
    1st : 2.733 (41/15T)
    2nd : 2.000 (38/19T)
    3rd : 1.590 (35/22T)
    4th : 1.333 (32/24T)
    5th : 1.153 (30/26T)
    6th : 1.035 (29/28T)
    Final Reduction Ratio;
    CBR250(F) : 2.500 (35/14T) – 520 Pitch
    CBR250R(H) : 3.142 (44/14T) – 520 Pitch
    CBR250R(J+K) : 3.176 (54/17T) – 428 Pitch
    CBR250RR(L+N+R) : 3.058 (52/17T) – 428 Pitch

    Cooling System
    Coolant Capacity :
    CBR250(F+H) : 1300cc (1100cc – Radiator, 200cc – Engine)
    CBR250R(J+K) : 1500cc (1300cc – Radiator, 200cc – Engine)
    CBR250RR(L+N+R) : 1570cc (1350cc – Radiator, 220cc – Engine)
    Coolant : 50% Distilled Water and 50% Pure Coolant (containing corrosion
    inhibiter, anti–freeze and anti–boil properties)
    Pressure Cap Opening;
    CBR250(F) + CBR250R(H) : 0.75 – 1.05kg/cm2
    CBR250R(J+K) : 0.95 – 1.25 kg/cm2
    CBR250RR(L+N+R) : 1.10 – 1.40kg/cm2
    Fan Switch;
    Cut In : 98 to 102oC
    Cut Out : 93 to 97oC
    Coolant Temperature Sensor Resistance at;
    50oC : 153.9W
    80oC : 51.9W
    120oC : 16.1W
    Thermostat;
    Opening Temp : 80 to 84oC
    Valve Lift : 8mm at 95oC

    Fuel
    Fuel Capacity;
    CBR250(F) + CBR250R(H) : 14 Litres + 2.5 Litre Reservoir
    CBR250R(J+K) : 13 Litres + 2 Litre Reservoir
    CBR250RR(L+N+R) : 13 Litres + 1.6 Litre Reservoir
    Fuel Grade : Unleaded min. 91 RON (Research Octane Number)
    Engine Idle Speed : 1,500rpm ± 100rpm

    Carburettor Synchronisation (max difference) : 40mmHg
    Carburettor ID Code (Keihin):
    CBR250(F) : VG01A
    CBR250R(H) : VG03A
    CBR250R(J+K) : VG05A
    CBR250RR(L+N) : VP20A
    CBR250RR® : VP20B
    Carburettor Throat Diameter :
    CBR250(F) : 25mm
    CBR250R(H) : 27mm
    CBR250R(J+K) : 28.5mm
    CBR250RR(L+N+R) : 29mm
    Float Heights (When measured at 30o or needle valve seated and spring NOT compressed):
    CBR250(F) : 7mm
    CBR250R(H) : 7mm
    CBR250R(J+K) : 8mm
    CBR250RR(L+N+R) : 13.7mm
    Carburettor Jet Sizes :
    CBR250(F) ;
    Main Jet : #85
    Pilot Jet : #35
    CBR250R(H);
    Main Jet : #88
    Pilot Jet : #35
    CBR250R(J+K);
    Main Jet : #85
    Pilot Jet : #35
    CBR250RR(L+N);
    Main Jet : Cylinders 1+4 : #105
    Cylinders 2+3 : #102
    Pilot Jet : #35
    CBR250RR®;
    Main Jet : Cylinder 1+4 : #112
    Cylinder 2+3 : #110
    Pilot Jet : #35
    Carburettor Pilot Screw Mixture Settings (Stock Air-Filter,Exhaust,Ports,Jets)
    CBR250(F) + CBR250R(H): 2Ѕ screws
    CBR250R(J+K) : 1 5/8 screws
    CBR250RR(L+N) : 1 3/4 screws
    CBR250RR® : 2 1/8 screws

    Suspension
    Fork Oil : 10W Fork Oil
    Fork Oil Height (from top when fork fully compressed with spring and spacer removed) :
    CBR250(F) : 114mm or 290ml ± 2.5ml
    CBR250R(H) : 100mm or 302ml ± 2.5ml
    CBR250R(J+K) : 95mm ± 6mm or 362ml ± 2.5ml
    CBR250RR(L+N+R) : 83mm or 383ml ± 2.5ml
    Fork Rake;
    CBR250(F) + CBR250R(H) : 26000’’
    CBR250R(J+K) : 25000’’
    CBR250RR(L+N+R) : 24000’’
    Fork Trail;
    CBR250(F) + CBR250R(H) : 97mm
    CBR250R(J+K) + CBR250RR(L+N+R) : 89mm
    Rear Shock Spring Free Length;
    CBR250(F) : 186.0mm ± 3.1mm
    CBR250R(H) : 175.0mm ± 3.1mm
    CBR250R(J+K) : 168.7mm ± 3.1mm
    CBR250RR(L+N+R) : 140.9mm ± 3.1mm

    Wheels
    Max Wheel Runout (front & back);
    Axial (side to side) : 2.0mm
    Radial (out of round) : 2.0mm
    Max Axial Runout (front & back) : 0.2mm

    Fuses
    Main/Ignition : 10Amp
    Headlights : 15Amp
    Tail Lights/Turn Signal Lights : 10Amp
    Fan : 10Amp

    Bulbs
    Headlights;
    Aust/UK : 60/55Watt H4 Halogen
    Japan : 60/35Watt Halogen
    Park Lights;
    Aust/UK : 5Watt
    Japan : 1.7Watt
    Brake/Tail Lights;
    Aust/UK : 21/5Watt
    Japan : 18/5Watt
    Turn Signal Lights;
    Aust/UK : 21Watt
    Japan : 15Watt
    Instrument Lights;
    Aust/UK : 3.4Watt
    Japan : 1.7Watt

    Ignition System
    General : Full transistor type battery firing (CDI)
    Firing Order : 1 – 2 – 4 – 3
    Ignition Timing;
    Idle (1,500rpm – Before Top Dead Centre);
    CBR250(F) + CBR250R(H) : 20o BTDC
    CBR250R(J+K) + CBR250RR(L+N): 23o BTDC
    CBR250RR® : 20o BTDC
    Full Advance : ???o BTDC

    Pulse Generator Coils Resistance;
    CBR250(F) + CBR250R(H+J+K) : 315 –385W @ 20oC
    CBR250RR(L+N+R) : 340 – 420W @ 20oC

    Ignition HT Coils :
    Primary Winding Resistance;
    CBR250(F) + CBR250R(H) : 2.6 – 3.2W @ 20oC
    CBR250R(J+K) : 2.52 – 3.08W @ 20oC
    CBR250RR(L+N+R) : 2.0 – 3.5W @ 20oC
    Secondary Winding Resistance (with plug caps and leads);
    CBR250(F) + CBR250R(H) : 21 – 29kW @ 20oC
    CBR250R(J+K) : 11.7 – 14.3kW @ 20oC
    CBR250RR(L+N+R) : 23 – 37kW @ 20oC
    Secondary Winding Resistance (without plug caps and leads);
    CBR250(F) + CBR250R(H) : 13 – 17kW @ 20oC
    CBR250R(J+K) : 11.7 – 14.3kW @ 20oC
    CBR250RR(L+N+R) : 13 – 17kW @ 20oC

    Electrical System
    Battery :
    CBR250(F) + CBR250R(H);
    Type : 12V 8Amp
    Current Leakage : 0.9Amp
    Voltage : 13.0 – 13.2 Volt @ 20oC
    CBR250R(J+K) + CBR250RR(L+N+R);
    Type : 12V 6Amp
    Current Leakage : 0.6Amp
    Voltage : 13.0 – 13.2 Volt @ 20oC

    Charging System;
    Current Leakage : 1mA (max)
    Regulator Voltage Output;
    CBR250(F) + CBR250R(H+J+K) : 14 – 15V @ 1,900rpm
    CBR250RR(L+N+R) : 14 – 15V @ 2,000rpm
    Regulator Current Output;
    CBR250(F) + CBR250R(H+J+K) : 18.5Amp @ 5,000rpm
    CBR250RR(L+N+R) : 270W @ 5,000rpm
    Stator Coil Resistance;
    CBR250(F) + CBR250R(H+J+K) : 0.3 – 0.4W @ 20oC
    CBR250RR(L+N+R) : 0.1 – 0.5W @ 20oC

    Miscellaneous
    Chain;
    CBR250(F) + CBR250R(H) : RK520??? or DID520???
    CBR250R(J+K) + CBR250RR(L+N+R) : RK428SMO or DID428VS1
    Chain Slack : 20 – 25mm

    Clutch Cable free play : 10 – 20mm
    Throttle Cable free play : 2 – 6mm

    Max. Brake Disc Warpage : 0.3mm
    Brake Disc Minimum Thickness : Stamped on Disc
    OR
    Front/Rear : 4.0mm
    Front/Rear – Service Limit : 3.5mm
    Rear – CBR250(F) ONLY – Drum Brake Diametre : 141.0mm

    Brake Disc Pad Minimum Thickness : 2.0mm
    Drum Brake Pad Minimum Thickness : CBR250(F) ONLY – 2.0mm


    Lubricants
    Brake Fluid : DOT4
    Chain Lubricant : SAE80 or 90 gear oil, aerosol chain lube for O–ring chains or chain saw oil.
    Steering Head Bearing : Lithium–based multi–purpose grease
    Wheel Bearings (unsealed, recommend using sealed) : Lithium–based Multi–purpose grease
    Swing–arm Pivot bearings : Molybdenum Disulphide grease
    Suspension Linkage bearings : Molybdenum Disulphide grease
    Bearing seal lips : Lithium–based multi–purpose grease
    Gear–change lever/Clutch level/Rear brake pivot : Molybdenum Disulphide grease or Dry film lubricant (graphite)
    Front brake lever/Calliper piston tip : Molybdenum Disulphide grease or Dry film lubricant (graphite)
    Cables : Cable lubricant or 10W40 motor oil
    Side–stand pivot : Molybdenum Disulphide grease
    Throttle Grip : Multi–purpose grease or Dry film lubricant (graphite)
     
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    Last edited: Aug 28, 2017
  2. Phil

    Phil Senior Member Premium Member Contributing Member

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    Very well put together, moucho info for the Cbr250's. :thumb_ups:
     
  3. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    I concur. Excellent Job Kiffsta.
     
  4. Mclaren

    Mclaren Well-Known Member Contributing Member

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    Cheers mate looking at mine while apart pilot factory but 1+4 are 105 and 2+3 are 108
     
  5. Glenn22

    Glenn22 Active Member

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    My Bike:
    83 RZ350 83 RZ250 87 TZR250 1KT RZF350 04 FZ6N 90 CBR250RR 95 TZR250SPR Sugo 12 KTM250 EXC
    According to the manual, outside cylinders 1 & 4 run 105 and the inside pair 2 & 3 are 102 standard, don't know why they're not around the other way, if the inner cylinders run a bit hotter surely bigger mains would help them run cooler ??
    The guy i bought my race bike off had purchased the 6 Sigma jet kit and it specs the bigger mains on the inside pair??
     
  6. Mclaren

    Mclaren Well-Known Member Contributing Member

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    Talking to Simon bigger in centre is what they all run bud
     
  7. Phil

    Phil Senior Member Premium Member Contributing Member

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    McLaren is correct, all the in-line fours run the larger jets on the 2 centre pots. I would put the 102 to the outer carbs and the 105 to the two centre carbs.
     
  8. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Phil,

    I thought the Honda ran the same across all 4 because it had a better airbox or something like that. Happy to be proven wrong. It always surprises me That a watercooled engine needs to run different main jets to "cool" a cylinder. It's not unheard of though. I had an XS400R parallel twin that ran a (much) bigger main jet on one carb than the other. That was due to the airbox inlet and filter placement. The XS400R was an oil-cooled bike though, so not sure what would have happened if it was water-cooled.
     
  9. Phil

    Phil Senior Member Premium Member Contributing Member

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    You could be on the money, I was under the impression all the in-line 4's used 2 bigger jets on the central pots and slightly smaller on the perimeter.
    Hey, what do I know, I ride them.
     
  10. Glenn22

    Glenn22 Active Member

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    So the manual is wrong then?
    CBR250RR(L+N);
    Main Jet : Cylinders 1+4 : #105
    Cylinders 2+3 : #102
     
  11. kiffsta

    kiffsta Administrator Staff Member Dirty Wheel Club Contributing Member

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    Manual is right , weird as other 250cc online 4 bikes are different
     
  12. Mclaren

    Mclaren Well-Known Member Contributing Member

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    Manual right but what I been told u go bigger in centre for racing
     
  13. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    I still think it has something to do with the airbox and/or high revving engines. In my mind, water-cooled should mean all cylinders are running at the same temp. Maybe the fairing shape also has something to do with airflow in and around the engine at high speed. What Mclaren said about bigger in the middle for racing might be true...engine revving its tits off in a straight line at high speeds might build up heat in the centre cylinders? All I know is people a lot smarter than me built these things and they didn't flip a coin and decide to have different sized jets just the fun of it. Do we have an engineer on this site?
     
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  14. Simon

    Simon Well-Known Member Premium Member Contributing Member

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    I'm definitely not an engineer frankster..but good to see you mate!! watercooled means all cylinders should be at the same temp..but the extra cooling from airflow around the sides of each block (call it 1/3 of swept volume at 250cc) and the abscence of the 'side' area to cool the head means that cyinders 2 and 3 run hotter as they have, by defenition reduced airflow over 1 and 4..ie lower surface area to dissapate heat..i can see why the inners will benefit from being cooler from running larger jets..on all engines i've built though the juries out..some benefit from smaller and some larger jets..a bigger factor is cylinder compression and valve clearances (aye call it wear lol!)..give an engine something combustable and with a spark to ignite then its all each to their own boss..I ran a cooling fan (as per dyno) in front of my old 72a and changed the jetting to suit and the inners were smaller than the outers for propper combustion..has honda got a point..i reckon the manuafcturers have a bit more guille than us too..go standard adjust from there and you wont be far wrong..to anyone who reads this invest in an exhaust gas anaylser..as its "right" for your bike..i've seen 28bhp translate into 43bhp just as a result of mapping the A/F ratio 100pc spot on..our engines are air pumps after all..if ur 1% out at idle thats multiplied by ten at peak power give or take..propper carb tune will reap BIG rewards guys!!!
     
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  15. Phil

    Phil Senior Member Premium Member Contributing Member

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    Simon
    Thanks a million for sharing your knowledge, think you have enlightened some of us.:thumb_ups:
     
  16. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    I am not adding anything to the discussion here except pointing out the differences in the models.
    From the parts book
    The L & N models are listed as
    Cyl 1 & 4 - #105
    Cyl 2 & 3 - #102
    The R & R-2 models are listed as
    Cyl 1 & 4 - #112
    Cyl 2 & 3 - #110
    [​IMG]
    The earlier models also run 2 shorter velocity stacks and 2 of the same length as the later models.

    The Yamaha FZR400 3TJ series also run smaller main jets on cylinder 2 & 3 and Dynojet also advise the same in one of their docs for Suzuki
    http://www.dynojet.com/pdf/European/Suzuki/E3149.003.pdf
    cheers
     
    Last edited: Nov 26, 2014
  17. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Hey Simon, Thanks for info. This thread has been enlightening for me too. I'm going to invest in an exhaust gas analyser. Moo also said these are essential to make sure everything is in the right ratio. Cheers
     
  18. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    For what it's worth, which is not much, I think the different jet size is just an attempt to broaden the smoothness of the engine running. Similar to the use of shorter and longer velocity stacks that some models run. In the FCR carbs fitted to the Yamaha FZR400SP (the racing model), the main jets are all the same size. If I were racing a 4 cylinder I would use the same jet size on all four cylinders.

    Regards the running hotter theory, the only real area of concern is the temperature of the combustion chamber. In a water cooled engine, hotspots, or areas of poor coolant circulation, would have a greater influence on variations in temperature than the external exposure of the cylinder head to airflow. I am not saying that there would be no effect from the outside temperature but rather that in a well designed water cooled engine the difference would be negligible. In short, without being able to take measurements it is really just speculation.
    cheers
     
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  19. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    Actually agree with this as I run the same main jets across all cylinders in the drag bike. Won't know if this is good or bad until it's fully sorted, but hasn't been an issue so far. The engine is at full revs for about 15 seconds; it gets warmish during the run, but cools down quickly after the run on the return road.
     
  20. Mclaren

    Mclaren Well-Known Member Contributing Member

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    Agree with water theory but as it. Runs to the centre some of the cooling affect has brendale used and also the obvious they in centre of engine and less air flow centre cyclinders would get hotter but jetting is a bike to bike thing mines it's from 12/13 thousand rpm to 17/18 for couple of laps few team tiger guys have same bigger in centre than outside however there size on both are different to mine
    Mine has been dyno tuned and exhaust gas analysed
     

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