A Clark G127 series industrial lift truck can be carried from routine tune-up to full engine overhaul on the strength of the 390 pages in this service manual PDF, which covers eight gas and LPG variants across the G127, GP127, GCS, GCX, GPS and GPX family. Overhaul chapters for the 4G32, 4G52 and 4G63 engines take up the largest share of the book, followed by transaxle teardown, main pump and valve rebuilds, tilt cylinders and triple stage upright shimming. At the back, wiring diagrams and hydraulic schematics trace the circuits through the lift cylinder, power steering valve and return line filter. Set initial timing on the 1.6 liter 4G32 to 5° BTDC at 700 to 750 rpm, and pull any fork whose heel has worn past 10%. Second shift, truck down, nobody to call. Search it, jump by bookmark, or print the pages you need and let them get greasy on your bench.
What's Inside This Clark G127/GP127/G127E/GP127E Manual
| System | Pages | Key Topics |
|---|---|---|
| How to Use This Manual | 3 | |
| Safety Signs and Safety Messages | 8-21 | Safety Signs, Safety Messages, Hazard Identification, Safety Precautions |
| Recommended Planned Maintenance and Lubrication Schedule | 22-37 | Planned Maintenance Program, Lubrication Chart, Miscellaneous Lubricants, Maintenance Intervals |
| Planned Maintenance Intervals | 39-43 | Daily Maintenance Checks, Periodic Checks, Maintenance Intervals, Operating Conditions |
| G32 Engine - 1.6 Liter | 44-86 | General Description, Engine Tune-Up, Engine Overhaul |
| G52 Engine - 2.0 Liter | 87-136 | - |
| G63 Engine - 2.0 Liter | 137-199 | Specifications and Description, Troubleshooting, Engine Overhaul |
| Engine Cooling System | 200-204 | Engine Overheating, Engine Overcooling, Water Pump Leakage, Water Pump Noise, Oil Contamination, Radiator, Radiator Cap, Fan Shroud, Radiator Hoses, Oil Cooler |
| Fuel System | 205-221 | Carburetor, Carburetor Overhaul, General Description |
| Transaxle (Transmission) | 222-258 | General Description, Transaxle Overhaul |
| Electrical | 259-278 | Distributor Overview, Distributor Inspection, Alternator Description, Alternator Overhaul, Starter Overview, Starter Assembly |
| Wheels and Tires | 279-296 | Drive Tire Specifications, Pneumatic Tire Maintenance, Safety Procedures |
| Hydraulic Brakes & Inching | 297-302 | General Description, Brake Master Cylinder Removal |
| Steering Gear | 303-314 | Steering Gear System, Steering Gear Overhaul |
| Power Steering System - Steer Axle | 315-323 | Power Steering System, Steer Axle Removal, Steer Axle Overhaul |
| Hydraulic System, Main Pump | 324-332 | Main Hydraulic System, Pump Overhaul |
| Main Hydraulic Valve | 333-337 | General Description, Main Valve Overhaul |
| Tilt Cylinder | 338-342 | Tilt Cylinder Adjustment, Tilt Cylinder Overhaul |
| Upright | 343-363 | Upright Maintenance, Upright Triple Stage Shim Disassembly |
| Counterweight | 364-367 | Counterweight Maintenance, Counterweight Installation |
| Machine Jacking & Blocking | 368-373 | Raising Drive Wheels, Blocking the Upright, Raising Entire Truck |
| Truck Data Plate and Decals | 374 | |
| Specifications | 375-378 | Fill Capacities |
| Hydraulic and Electrical Diagrams | 379-390 | Lift Cylinder, Tilt Cylinders, Power Steering Valve, Main Hydraulic Valve, Return Line Filter |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Maximum fork tip height difference | 3% of the fork length | p. 27 |
| Maximum fork blade heel wear | 10% | p. 27 |
| Initial (Basic) Ignition Timing | 5° BTDC @ 700-750 rpm | p. 51 |
| Engine Idle Speed | 650-750 rpm | p. 49 |
| Engine Idle Speed (4G63) | 650-700 rpm | p. 144 |
| Engine Sump Capacity | 4.5 L (4.8 qt) | p. 143 |
| LPG safety relief valve pressure | 275 psi | p. 217 |
| Radiator hose clearance | 15 mm (0.59 inch) | p. 201 |
| Hose to fan and alternator belt gap | 25 mm (1.00 inch) | p. 202 |
| Engine Oil Capacity (4G63) | 4.5 L | p. 143 |
| Cylinder Head Bolt Tightening Torque (4G63 Cold) | 88-98 N·m | p. 110 |
| Cylinder Head Bolt Tightening Torque (4G63 Warm) | 98-108 N·m | p. 110 |
Clark G127/GP127/G127E/GP127E Common Problems This Manual Covers
Clark G127 lift truck G32 1.6 liter engine hard starting, stalling, or missing
Check initial ignition timing against 5° BTDC at 700-750 rpm following page 51, then verify idle speed holds 650-750 rpm per page 49. Work through the hard starting, stall, and miss charts on page 81 before tearing into anything. When you pull the plugs, torque them back to 2.5-3.0 kg.m (18-21 lbf-ft) per page 64.
Manual Section: G32 Engine - 1.6 Liter p. 81G63 2.0 liter engine with irregular idling, uneven running, erratic firing, or lack of power
Measure the ignitor air gap and set it to 0.8 mm (.031 in) following page 144, then verify idle speed lands in the 650-700 rpm window listed on that same page. Check oil level against the 4.5 L (4.8 qt) sump capacity on page 143. Work the G63 troubleshooting charts in the engine section before replacing parts.
Manual Section: G63 Engine - 2.0 Liter p. 137Engine running too hot, water pump leaking or noisy, and oil showing up in the coolant
Test the radiator cap against the 14 psi rating (12-16 psi range) listed on page 375 before you blame the pump. Check that the radiator hoses keep at least 25 mm (1.00 inch) of clearance from the fan and the alternator belt per page 202. Match pump leaks, pump noise, and oil in coolant to their causes on page 200.
Manual Section: Cooling System - Troubleshooting p. 200Transaxle showing low clutch pressure, low converter out pressure, overheating, or loss of power
Check the transaxle cooling line hose ends for weeping and torque them to 40-45 N·m (30-33 lbf-ft) following page 203. Then work the transmission troubleshooting chart in the section starting on page 222. Match low clutch pressure, low converter out pressure, overheating, or noise to its listed cause before you pull the transaxle.
Manual Section: Transaxle (Transmission) p. 222Steering with high handwheel effort, kickback, slow response, or a free spinning handwheel
Verify steering system relief pressure at the priority demand valve against 8274-8963 kPa (1200-1300 psi) following page 303. That valve is set at a fixed value, so a reading outside that band tells you something. Then inspect the steering gear against the troubleshooting chart for high handwheel turns, wrong direction, and kickback before pulling the gear for overhaul.
Manual Section: Steering Gear p. 303Main hydraulic pump noisy, foaming oil, running hot, or failing to build pressure
Check the hydraulic sump oil level first; the tank holds 30.3 L (8 gal) total volume per page 375. Inspect the pump shaft seal and external fittings for leakage. Then work the pump troubleshooting chart for low output and failure to build pressure before you start the pump overhaul in the section beginning on page 324.
Manual Section: Hydraulic System, Main Pump p. 324Frequently Asked Questions
What is the cylinder head bolt torque spec for the 4G32 engine in the Clark G127/GP127/G127E/GP127E?
For the 4G32 engine, the cylinder head bolt tightening torque is 68-74 N.m (51-54 lbf.ft) when cold, and 78-83 N.m (58-61 lbf.ft) when warm. p. 52
What is the recommended engine oil for the 4G63 Gas & LPG engine?
The recommended engine oil for the 4G63 engine is 10W30, API CC, CD/SG, SF engine oil. The sump capacity is 4.5 liters (4.8 quarts). p. 143
How do I check the transmission clutch disc clearance on a Clark G127/GP127/G127E/GP127E lift truck?
Stand the clutch assembly on end so the discs fall to the end plate. Measure the distance between the clutch piston and the first steel disc using a feeler gauge through the slots in the clutch drum. The required clearance is 1.22-2.66 mm (0.048-0.105 in). p. 240
What spark plug gap is specified for the 4G32 engine in the Clark G127/GP127/G127E/GP127E lift truck?
The spark plug gap for the 4G32 engine should be set between 0.7 and 0.8 mm (0.027-0.031 inch). p. 50
How do I adjust the steering system relief pressure?
The steering system relief pressure is controlled by a priority demand valve set at a fixed value of 8274-8963 kPa (1200-1300 psi). No service adjustment of this pressure can be made; if the pressure is not correct, the priority demand valve should be replaced. p. 303
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