motorcycle mechanics institute: Technical Information – Air Inlet System

Sub Throttle Control System

The ZR750–J1 employs large bore throttle bodies to increase power output. However, sudden changes in throttle opening can cause hesitation and jerky throttle response with a single butterfly valve in a large bore. Therefore two throttle valves are placed in each inlet tract, the main throttle valve located closest to the cylinder and a subthrottle valve placed further up the inlet tract. The main throttle valve is operated by the rider when the throttle grip is turned clockwise or counterclockwise, while the subthrottle valve is operated by a stepping motor controlled by the ECU. The subthrottle valve automatically adjusts air inlet to more precisely match engine demand, so that when the main throttle is opened quickly there is no hesitation or jerky response. The subthrottle valves allow the fuel injection system to provide smooth throttle response, similar to that of a constant velocity carburetor, no matter how quickly the throttle is opened.

A. Main Throttle Valve
B. Subthrottle Valve
C. Throttle Valve
D. Vacuum Piston
E. Inlet Air

Operation

The subthrottle control system consists of the subthrottle valve, subthrottle valve actuator with a stepping motor built in it, ECU, and subthrottle sensor. The subthrottle valve is built in the each throttle body.

The subthrottle control system operates on the signal supplied from the ECU. The open/close operation of the subthrottle valve is performed by the subthrottle actuator which is controlled by the ECU to change the current direction into the motor of the subthrottle valve actuator. The subthrottle sensor detects the subthrottle valve actuator movement by measuring voltage and the ECU determines the subthrottle valve angle based on the operation map. When turning the ignition switch ON, every time the ECU automatically drives the subthrottle valve from fully closed position to fully opened position. The ECU memorizes these positions and turns back the subthrottle valve to the original point to confirm the subthrottle valve idling voltage.

A. Subthrottle Valves
B. Subthrottle Valve Actuator
C. Subthrottle Sensor
D. Main Throttle Sensor
E. ECU (Electric Control Unit)
F. Air Cleaner Side
G. Crankshaft Sensor
H. Speed Sensor

motorcycle mechanics institute: General Specifications

ZR750–J1	Items
2 080 mm (81.9 in.) 780 mm (30.7 in.) 1 055 mm (41.5 in.) 1 425 mm (56.1 in.) 165 mm (6.5 in.) 815 mm (32.1 in.) 195 kg (430.0 lb) 111 kg (244.8 lb) 107 kg (235.9 lb) 18 L (5.0 US gal.)	Dimensions: Overall length Overall width Overall height Wheelbase Road clearance Seat height Dry mass Curb mass:                 Front                                     Rear Fuel tank capacity
2.9 m (9.5 ft)	Performance: Minimum turning radius
4-stroke, DOHC, 4-cylinder Liquid-cooled 68.4 × 50.9 mm (2.7 × 2.0 in.) 748 mL (45.64 cu in.) 11.3 79 kW (107 PS) @10 500 r/min (rpm), (MY, AU) 80 kW (109 PS) @11 000 r/min (rpm) (HR) 78.2 kW (106 PS) @11 000 r/min (rpm) 75 N·m (7.6 kgf·m, 55 ft·lb) @8 200 r/min (rpm), (HR) 73 N·m (7.4 kgf·m, 54 ft·lb) @8 200 r/min (rpm) FI (Fuel Injection) KEIHIN TTK34 × 4 Electric starter Battery and coil (transistorized) Electronically advanced (digital igniter) From 10° BTDC @1 100 r/min (rpm) to 37° BTDC @5 800 r/min (rpm) NGK CR9EK or ND U27ETR Left to right, 1-2-3-4 1-2-4-3 38° BTDC 66° ABDC 284° 57° BBDC 31° ATDC 268° Forced lubrication (wet sump) API SE, SF or SG API SH or SJ with JASO MA SAE 10W-40 3.8 L (4.0 US qt)	Engine: Type Cooling system Bore and stroke Displacement Compression ratio Maximum horsepower Maximum horsepower Carburetion system Starting system Ignition system Timing advance Ignition timing Spark plug Cylinder numbering method Firing order Valve timing:       Inlet                   Open                                   Close                                 Duration       Exhaust            Open                                   Close                                 Duration Lubrication system Engine oil: Type Viscosity Capacity
Gear 1.714 (84/49) Wet multi disc 6-speed, constant mesh, return shift 2.571 (36/14) 1.941 (33/17) 1.555 (28/18) 1.333 (28/21) 1.200 (24/20) 1.095 (23/21) Chain drive 2.867 (43/15) 5.382 @Top gear	Drive Train: Primary reduction system:     Type Reduction ratio Clutch type Transmission: Type Gear ratios:   1st                       2nd                       3rd                       4th                       5th                       6th Final drive system: Type Reduction ratio Overall drive ratio
Tubular, diamond 24.5° 104 mm (4.1 in.) Tubeless 120/70 ZR17 M/C (58W) Tubeless 180/55 ZR17 M/C (73W) Telescopic fork (upside-down) 120 mm (4.7 in.) Swingarm (uni-trak) 126 mm (5.0 in.) Dual discs Single disc	Frame: Type Caster (rake angle) Trail Front tire:        Type                         Size Rear tire: :        Type                         Size Front suspension: Type                         Wheel travel Rear suspension: Type                         Wheel travel Brake Type:    Front                         Rear
12 V 8 Ah Semi-sealed beam 12 V 55 W × 2/55 W (Hi/Lo) 12 V 0.5/3.8 W (LED), (CA) 12 V 0.5/5W (LED) Three-phase AC 24 A/14 V @5 000 r/min (rpm)	Electrical Equipment: Battery Headlight:        Type                          Bulb Tail/brake light Alternator:     Type                       Rated output

Specifications are subject to change without notice, and may not apply to every country.

(AU): Australia Model

(CA): Canada Model

(MY):Malaysia Model

(HR): with Honeycomb Catalytic Converter Model (Restricted model)

motorcycle mechanics institute: Model Identification

ZR750–J1 Left Side View:

ZR750–J1 Right Side View:

motorcycle mechanics institute: Before Servicing

Before Servicing

Before starting to perform an going over service or carry out a disassembly and reassembly operation on a motorcycle, read the precautions given below. To assist actual operations, notes, illustrations, Photographs, cautions, and complete imagery have been included in each chapter wherever Necessary. This sector explains the items that require scrupulous attention during the removal and Reinstallation or disassembly and reassembly of general parts. particularly note the subsequent:

Battery Ground
Before completing any service on the motorcycle, disconnect the battery wires from the battery to prevent the steam engine from accidentally whirling over. Disconnect the ground wire (–) first and then the positive (+). When fulfilled with the service, first connect the positive (+) wire to the positive (+) terminal of the battery then the negative (–) wire to the negative life-threatening.

Edges of Parts
pinch large or heavy parts taxing gloves to thwart injury from potential sharp limits on the parts.

Solvent
Use a high flush point in the money when attack parts. High flush point solvent should be used according to commands of the solvent manufacturer.

Cleaning vehicle before disassembly
Clean the vehicle thoroughly before disassembly. Dirt or other foreign materials entering into sealed areas during vehicle disassembly can cause excessive wear and decrease performance of the vehicle. 

Arrangement and Cleaning of Removed Parts
Disassembled parts are easy to confuse. Arrange the parts according to the order the parts were disassembled and clean the parts in order prior to assembly.

Storage of Removed Parts

After all the parts including subassembly parts have been cleaned, store the parts in a clean area. Put a clean cloth or plastic sheet over the parts to protect from any foreign materials that may collect before re-assembly.

Inspection
Reuse of worn or damaged parts may lead to serious accident. Visually inspect removed parts for corrosion, discoloration, or other damage. Refer to the appropriate sections of this manual for service limits on individual parts. Replace the parts if any damage has been found or if the part is beyond its service limit.

Replacement Parts

Replacement parts must be KAWASAKI genuine or recommended by KAWASAKI. Gaskets, O-rings, oil seals, grease seals, circlips or cotter pins must be replaced with new ones whenever disassembled.

Assembly Order

In most cases assembly order is the reverse of disassembly, however, if assembly order is provided in this Service Manual, follow the procedures given.

Tightening Sequence

Bolts, nuts, or screws must be tightened according to the specified sequence to prevent case warpage or deformation which can lead to malfunction. If the specified tightening sequence is not indicated, tighten the fasteners alternating diagonally.

Tightening Torque

Incorrect torque applied to a bolt, nut, or screw may lead to serious damage. Tighten fasteners to the specified torque using a good quality torque wrench. Often, the tightening sequence is followed twice-initial tightening and final tightening with torque wrench.

Force

Use common sense during disassembly and assembly, excessive force can cause expensive or hard to repair damage. When necessary, remove screws that have a non -permanent locking agent applied using an impact driver. Use a plastic-faced mallet whenever tapping is necessary.

Gasket, O-ring

Hardening, shrinkage, or damage of both gaskets and O-rings after disassembly can reduce sealing performance. Remove old gaskets and clean the sealing surfaces thoroughly so that no gasket material or other material remains. Install new gaskets and replace used O-rings when re-assembling

Liquid Gasket, Locking Agent

For applications that require Liquid Gasket or a Locking agent, clean the surfaces so that no oil residue remains before applying liquid gasket or locking agent. Do not apply them excessively. Excessive application can clog oil passages and cause serious damage.

Press

For items such as bearings or oil seals that must be pressed into place, apply small amount of oil to the contact area. Be sure to maintain proper alignment and use smooth movements when installing.

Ball Bearing and Needle Bearing

Do not remove pressed ball or needle unless removal is absolutely necessary. Replace with new ones whenever removed. Press bearings with the manufacturer and size marks facing out. Press the bearing into place by putting pressure on the correct bearing race as shown. Pressing the incorrect race can cause pressure between the inner and outer race and result in bearing damage.

Oil Seal, Grease Seal

Do not remove pressed oil or grease seals unless removal is necessary. Replace with new ones whenever removed. Press new oil seals with manufacture and size marks facing out. Make sure the seal is aligned properly when installing.

Circlips, Cotter Pins

Replace circlips or cotter pins that were removed with new ones. Install the circlip with its sharp edge facing outward and its chamfered side facing inward to prevent the clip from being pushed out of its groove when loaded. Take care not to open the clip excessively when installing to prevent deformation.

Lubrication

It is important to lubricate rotating or sliding parts during assembly to minimize wear during initial operation. Lubrication
points are called out throughout this manual, apply the specific oil or grease as specified.

Direction of Engine Rotation

When rotating the crankshaft by hand, the free play amount of rotating direction will affect the adjustment. Rotate
the crankshaft to positive direction (clockwise viewed from output side).

Electrical Wires

A two-color wire is identified first by the primary color and then the stripe color. Unless instructed otherwise, electrical wires must be connected to those of the same color.