The Kawasaki 900cc Four Cylinder Models, specifically the Z1 and Z1A, are high-performance motorcycles designed for enthusiasts. This manual provides comprehensive details on their function, technical specifications, usage, and maintenance.
Function Description:
The Kawasaki 900cc models are powered by a four-cylinder engine, designed for smooth and powerful operation. The engine utilizes a dual overhead camshaft (DOHC) system, timed and driven by a roller drive chain from the crankshaft. The camshaft lobes directly act on valve lifter shims to operate the valves, ensuring precise valve timing. Fuel delivery is managed by four Mikuni type VM28SC carburetors, which are crucial for optimal engine performance. The ignition system is battery and coil type, with breaker points mounted on the crankshaft and a three-phase alternator for electrical power generation. An electronic voltage regulator and full-wave rectifier manage the electrical system, which is protected by a 20A fuse. The motorcycle features a wet sump lubrication system, where oil is drawn from the sump by an oil pump, filtered, and then distributed to critical engine components like crankshaft main bearings, camshaft bearing holders, and transmission shaft bearings. A separate small oil pump lubricates the rear drive chain. The transmission is a five-speed unit, incorporating a neutral finder mechanism built into the output shaft. The clutch is a multiple-disc, wet-type system, allowing for smooth power transfer. The front suspension consists of hydraulic disc brakes and fork units, while the rear suspension units are designed for durability.
Important Technical Specifications:
- Engine: Four-cylinder, 903cc displacement.
- Bore & Stroke: 66mm x 66mm.
- Ignition: Spark plug NGK type B-8ES.
- Spark Plug Electrode Gap: 0.7-0.8mm (0.028-0.031 inch).
- Point Gap: 0.3-0.4mm (0.012-0.016 inch).
- Firing Order: 1-2-4-3.
- Valve Clearance (cold): 0.05-0.10mm (0.002-0.004 inch).
- Electrical System: 12V, negative grounded.
- Battery: 12V 14AH.
- Tire Size: Front 3.25 x 19, Rear 4.00 x 18.
- Tire Pressure: Front 1.8 kg/cm² (26 psi), Rear 2.2 kg/cm² (31 psi). Rear tire pressure should be increased to 2.5 kg/cm² (36 psi) when carrying a passenger.
- Rear Chain Free Play: 45mm (13/4 inch), checked on center stand.
- Carburetors: Mikuni type VM28SC.
- Main Jet: #112.5.
- Needle Jet: P-9.
- Jet Needle: 5J9.
- Pilot Jet: #20.
- Throttle Slide: 2.5.
- Jet Needle Clip: Third groove from top.
- Float Level: 24mm (0.9449 inch).
- Engine Oil Capacity: 4000cc.
- Recommended Engine Oil: SAE 10W/40, 10W/50, or 20W/50 (service SE or SD).
- Engine Oil Pressure: Approximately 0.2 kg/cm² (2.84 psi) @ 3000 rpm with oil temperature at 60°C (140°F).
- Front Fork Oil Capacity: 169cc per unit.
- Recommended Front Fork Oil: SAE 10W motor oil.
- Front Fork Oil Level: 455mm (17.91 inch) from top of fork tube.
- Valve Stem Diameter: Intake 6.925-6.980 inch (0.2742-0.2748 inch), Exhaust 6.955-6.970mm (0.2738-0.2744 inch).
- Valve Guide Inside Diameter: All 7.000-7.015mm (0.2755-0.2761 inch).
- Valve Spring Free Length: Inner 36.0mm (1.417 inch).
- Maximum Cylinder Head Warpage: 0.25mm (0.0098 inch).
- Camshaft Lobe Height: Intake 36.25-36.34mm (1.427-1.430 inch), Exhaust 35.76-35.84mm (1.407-1.411 inch).
- Camshaft Bearing Clearance: 0.020-0.064mm (0.0008-0.0025 inch).
- Camshaft Journal Diameter: 24.467-24.480mm (0.9633-0.9637 inch).
- Maximum Camshaft Runout: 0.10mm (0.0039 inch).
- Standard Cylinder Bore Diameter: 66.000-66.019mm (2.5984-2.5992 inch).
- Standard Piston Skirt Diameter: 65.93-65.95mm (2.5956-2.5964 inch).
- Recommended Piston Skirt to Cylinder Clearance: 0.060-0.079mm (0.0023-0.0031 inch).
- Piston Ring End Gap: 0.2-0.4mm (0.0078-0.0157 inch).
- Piston Ring Clearance in Groove: Top ring 0.045-0.080mm (0.0017-0.0031 inch), Second & oil ring 0.010-0.050mm (0.004-0.0019 inch).
- Connecting Rod Side Clearance: 0.3-0.4mm (0.0118-0.0157 inch).
- Connecting Rod Radial Clearance: 0.08mm (0.0031 inch).
- Crankshaft Runout: 0.10mm (0.0039 inch).
- Clutch Friction Disc Thickness: 3.7-3.9mm (0.1456-0.1535 inch).
- Clutch Spring Free Length: 33.8mm (1.330 inch).
- Brake Disc Runout: 0.3mm (0.0118 inch).
- Brake Disc Thickness: Minimum 5.5mm (0.2165 inch).
- Master Cylinder Internal Diameter: 14.000-14.043mm (0.5512-0.5529 inch).
- Piston Diameter (Master Cylinder): Minimum 13.960mm (0.5496 inch).
- Master Cylinder Return Spring Free Length: 48mm (1.889 inch).
Usage Features:
- Carburetor Synchronization: Essential for smooth engine performance. Adjustments should be made with the engine at normal operating temperature, ensuring all carburetors are set alike. Vacuum gages are recommended for precise synchronization, aiming for equal vacuum readings across all cylinders (20-23 cm Hg or 8-9 inch Hg).
- Ignition Timing: Adjustable by setting breaker point gap and aligning timing marks. A power timing light is used to check ignition timing at idle speed and full advance. Early type advancer mechanisms reach full advance at approximately 3000 rpm, while late type mechanisms reach full advance at approximately 2350 rpm.
- Clutch Adjustment: The clutch cable free play should be 2-3mm (0.08-0.12 inch) at the handlever pivot.
- Brake System: Hydraulic disc brakes are fitted on the front wheel. Only DOT 3 brake fluid should be used. The system must be bled of air if any fittings are loosened or if the fluid level drops below limits.
- Fuel Level Check: Can be performed without removing carburetors by using a sight gage attached to the drain plug hole. The fuel level should be 3.5mm (0.137 inch) below the edge of the throttle body.
Maintenance Features:
- Spark Plug: Replace with NGK type B-8ES or equivalent, setting the electrode gap to 0.7-0.8mm (0.028-0.031 inch).
- Carburetors: Regular cleaning and adjustment are necessary. Pilot air screws are initially set to 1½ turns out from a lightly seated position. Idle speed is adjusted to approximately 1000 rpm.
- Valve Clearance: Measured with the engine cold and adjusted by installing shims of various thicknesses on top of valve lifters. A special tool (#57001-109) can be used to hold the lifter down for shim access.
- Cam Chain Tension: Adjusted at regular intervals or when excessive noise is heard. Loosen the lock nut and set bolt, then turn the engine through several revolutions to allow the spring tensioner to set the chain tension.
- Engine Oil: Drain and renew every 2000 miles. Maintain oil level at the top mark near the sight glass.
- Oil Filter: Renew every other oil change.
- Rear Drive Chain Lubrication: Service with SAE 90 gear oil. The pump output can be varied by adjusting the pump adjuster arm.
- Front Forks: Check oil level (455mm from top of fork tube) and replace oil if necessary. Oil can be drained by removing the drain screw and pumping the front of the motorcycle.
- Cylinder Head and Valves: Valve guides should be renewed if worn, and the cylinder head heated to 120-150°C (250-300°F) for removal and installation.
- Pistons and Cylinders: Pistons and rings are available in oversizes. Piston rings should be installed with markings toward the top and pistons with the arrow on the dome toward the exhaust.
- Crankshaft and Connecting Rods: Inspect for wear and damage. The center crankshaft main bearing cap should be installed with the arrow toward the front of the engine and bolts tightened in sequence.
- Transmission: Inspect gears for damage and check backlash. Shift forks should be renewed if bent, discolored, or excessively worn.
- Oil Pump: Inspect clearance between pump housing and gears. Renew as an assembly if excessively worn.
- Clutch: Inspect friction discs for warping and wear. Renew if thickness is less than 3.4mm (0.133 inch). Check clutch springs for free length and renew if less than 32.3mm (1.271 inch).
- Disc Brake Caliper: Inspect internal diameter and piston for wear. Renew if scratched, pitted, or worn beyond limits. Clean all parts with alcohol and lubricate with clean brake fluid.
- Brake Disc: Renew if badly scored or worn to a thickness less than 5.5mm (0.2165 inch).
- Master Cylinder: Inspect internal diameter and piston for wear. Renew if scratched, pitted, or worn beyond limits. Rubber parts should be renewed if swollen, cracked, or rotted.
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