| LOST POWER AND OVERHEATING |
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| PART AFFECTED | NATURE OF TROUBLE | SYMPTOMS AND EFFECTS | REMEDY |
| Water Pipe Joint. | Loose. | Loss of water, heating. | Tighten bolts, replace gaskets. |
| Spark Plug. | Leakage in threads, insulation, or packing. | Loss of power. Hissing caused by escaping gas. | Replace insulation if defective, screw down tighter. |
| Compression Release Cock. | Leak in threads. Leak in fitting. | Loss of power. Whistling or hissing. | Tighten if loose. Grind fitting to new seating in body. |
| Combustion Chamber. | Crack or blowhole. Roughness. Carbon deposits. Sharp edges. | Loss of compression. Preignition. | Fill by welding. Smooth out roughness. Scrape out or dissolve carbon. |
| Valve Chamber Cap. | Leak in threads. Defective gasket. | Loss of compression. Hissing. | Remove. Apply pipe compound to threads and replace. Use new gasket or packing. |
| Valve Head. | Warped. Scored or pitted. Carbonized. Covered with scale. Loose on stem (two-piece valves only). | Loss of compression. | True up in lathe. Grind to seat. Scrape off. Smooth with emery cloth. Tighten by riveting. |
| Valve Seat. | Warped or pitted. Covered with carbon. Foreign matter between valve and seat. | Loss of compression. | Use reseating reamer. Clean off and grind valve to seat. |
| Valve Stem. | Covered with scale. Bent. Binding in guide. Stuck in guide. | Valve does not close. Loss of compression. | Clean with emery cloth; straighten. True up and smooth off. free with kerosene. |
| Valve Stem Guide. | Burnt or rough. Loose in valve chamber. | Valve may stick. Action irregular. | Clean out hole. Screw in tighter. |
| Valve Spring. | Weak or broken. | Valve does not close. | |
| Valve Operating Plunger. | Loose in guide. Too much clearance between valve stem. | Valve action poor. Lift insufficient. | Replace with new. Adjust screw closer. |
| Valve Lift Adjusting Screw. | Threads stripped. Too near valve. Too far from valve. | Poor valve action. | Replace with new. Adjust with proper reference to valve stem. |
| Valve Lift Cam. | Worn cam contour. Loose on shaft. Out of time. | Not enough valve lift. Will not lift valve. Valve opens at wrong time. | Replace with new. Replace pins or keys. Set to open properly. |
| Cam-shaft. | Sprung or twisted. | Valves out of time. | Straighten. |
| Cam-shaft Bushing. | Worn. | Not enough valve lift. | Replace. |
| Cam-shaft Drive Gear. | Loose on shaft. Out of time. Worn or broken teeth. | Irregular valve action. | Fasten securely. Time properly. Replace with new. |
| Cam Fastenings. | Worn or broken. | Valves out of time. | Replace with new. |
| Cylinder Wall. | Scored, gas leaks. Poor lubrication causes friction. | Poor compression. Overheating. | Grind out bore. Repair oiling system. |
| Piston. | Binds in cylinder. Walls scored. Worn out of round. | Overheating. Poor compression. | Lap off excess metal. Replace with new. |
| Piston Rings. | Loss of spring. Loose in grooves. Scored. Worn or broken. Slots in line. | Loss of compression. Gas blows by. | Peen ring or replace. Fit new rings. Grind smooth. Replace. Turn slots apart. |
| | Carbon in grooves. Insufficient opening. Binding on cylinder. | Overheating because of friction. | Remove deposits. File slot. Grind or lap to fit cylinder bore. |
| Wristpin. | Loose, scores cylinder. | Loss of compression. | Fasten securely. Replace cylinder if groove is deep. |
| Crank-shaft. | Scored or rough on journals. Sprung. | Overheating because of friction. | Smooth up. Straighten. |
| Crank Bearings. Main Bearings. | Adjusted too tight. Defective oiling. Brasses burned. | Overheating because of friction. | Adjust freely, clean out oil holes and enlarge oil grooves. |
| Oil Sump. | Insufficient oil. Poor lubricant. Dirty oil. | Overheating. | Replenish supply. Use best oil. Wash out with kerosene; put in clean oil. |
| Water Space. Water Pipes. | Clogged with sediment or scale. | Overheating. | Dissolve foreign matter and remove. |
| Piston Head. | Cracked (rare). Carbon deposits. | Loss of compression. Preignition. | Weld by autogenous process. Scrape off carbon accumulations. |
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| NOISY OPERATION OF POWER PLANT |
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| PART AFFECTED | NATURE OF TROUBLE | CHARACTER OF NOISE | REMEDY |
| Compression Release Cock. | Leakage. | Hissing. | Previously given. |
| Spark Plug. | Leakage. | Hissing. | Previously given. |
| Valve Chamber Cap. | Leakage. | Hiss or whistle. | Previously given. |
| Combustion Chamber. | Carbon deposits. | Knocking. | Previously given. |
| Inlet Valve Seat. | Defects previously given. | Popping in carburetor. | Previously given. |
| Valve Head. | Loose on stem. | Clicking. | Previously given. |
| Valve Stem. Valve Stem Guide. | Wear or looseness. | Rattle or clicking. | Previously given. |
| Inlet Valve. | Closes too late. Opens too early. | Blowback in carburetor. | Previously given. |
| Valve Spring. | Weak or broken. | Blowback in carburetor. | Previously given. |
| Cylinder Casting. | Retaining bolts loose. Piston strikes at upper end. | Sharp metallic knock. | Tighten bolts. Round edges of piston top. |
| Cylinder Wall. | Scored. | Hissing. | Previously given. |
| Valve Stem Clearance. | Too much. Too little (inlet valve). | Clicking. Blowback in carburetor. | Previously given. |
| Valve Operating Plunger. Plunger Guide. | Looseness. | Rattle or clicking. | Previously given. |
| Timing Gears. | Loose on fastenings. Worn teeth. Meshed too deeply. | Metallic knock. Rattle. Grinding. | Previously given. |
| Cylinder or Piston. | No oil, or poor lubricant. | Grinding. | Repair oil system. |
| Cam. | Loose on shaft. Worn contour. | Metallic knock. | Previously given. |
| Cam-shaft Bearing. | Looseness or wear. | Slight knock. | Previously given. |
| Cam Fastening. | Looseness. | Clicking. | Previously given. |
| Piston. | Binding in cylinder. Worn oval, causes side slap in cylinder. | Grinding or dull squeak. Dull hammering. | Previously given. |
| Piston Head. | Carbon deposits. | Knocking. | Previously given. |
| Piston Rings. | Defective oiling. Leakage. Binding in cylinder. | Squeaking. Hissing. Grinding. | Previously given. |
| Wrist-pin. | Loose in piston. Worn. | Dull metallic knock. | Replace with new member. |
| Connecting Rod. | Wear in upper bushing. Wear at crank-pin. Side play in piston. | Distinct knock. | Adjust or replace. Scrape and fit. Use longer wrist-pin bushing. |
| Crank Bearings. | Looseness. Excessive end play. Binding, fitted too tight. | Metallic knock. Intermittent knock. Squeaking. | Refit bearings. Longer bushings needed. Insert shims to allow more play. |
| Main Bearings. | Looseness. Defective lubrication. | Metallic knock. Squeaking. | Fit brasses closer to shaft. Clean out oil holes and grooves. |
| Connecting Rod Bolts. Main Bearing Bolts. | Loose. | Sharp knock. | Tighten. |
| Crank-shaft. | Defective oiling. | Squeaking. | Previously given. |
| Engine Base. | Loose on frame. | Sharp pounding. | Tighten bolts. |
| Lower Half Crank-case. | Bolts loose. | Knocking. | Tighten bolts. |
| Fly-wheel. | Loose on crank-shaft. | Very sharp knock. | Tighten retention bolts or fit new keys. |
| Oil Sump. | Oil level too low. Poor lubricant. | Grinding and squeak in all bearings. | Replenish with best cylinder oil. |
| Valve Plunger Retention Stirrups. | Looseness. | Clicking. | Tighten nuts. |
| Fan. | Blade loose. Blade strikes cooler. | Clicking or rattle. | Tighten. Bend back. |
| Exhaust Pipe Joints. | Leakage. | Sharp hissing. | Tighten or use new gasket. |
| Crank-case Packing. | Leakage. | Blowing sound. | Use new packing. Tighten bolts. |
| Water Pipe. | Leaks. Loss of water. Clogged with sediment. | Pounding because engine heats. | Previously given. |
| Water Jacket. | Clogged with sediment. Walls covered with scale. | Knocking because engine heats. | Dissolve scale and flush out water space with water under pressure. |
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| “SKIPPING” OR IRREGULAR OPERATION |
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| PART AFFECTED | NATURE OF TROUBLE | SYMPTOMS AND EFFECTS | REMEDY |
| Compression Relief Cock. | Leak in threads or spigot. | Dilutes mixture with air, causes blowback. | Screw down tighter. Grind spigot to seat with emery. |
| Spark-Plug. | Leak in threads. Defective gasket. Cracked insulator. Points too near. Points covered with carbon.Too much air gap. | Dilutes mixture. Allows short circuit. No spark. | Screw down tighter. Replace with new. Set points 1⁄64′′ apart for magneto, 1⁄32′′ for battery spark. |
| Valve Chamber Cap. | Leak in threads. Defective gasket. | Dilutes mixture by allowing air to enter cylinder on suction stroke. | Previously given. |
| Combustion Chamber. | Carbon deposits. | Preignition. | Scrape out. |
| Valve Head. | Warped or pitted. Loose on stem. | Dilutes charge with poor air or gas. | Previously given. |
| Valve Stem. | Binding in guide. Sticking. | Irregular valve action. | Previously given. |
| Valve Seat. | Scored or warped. Cracked. Covered with scale. Dirt under valve. | Gas leak, poor mixture. Poor compression. Valve will not close. | Previously given. |
| Induction Pipe. | Leak at joints. Crack or blowhole. | Mixture diluted with excess air. | Stop all leaks. |
| Inlet Valve. | Closes too late. Opens too early. | Blowback in carburetor. | Time properly. |
| Exhaust Valve. | Opens too late. Closes too early. | Retention of burnt gas dilutes charge. | Time properly. |
| Valve Stem Guide. | Bent or carbonized. | Causes valve to stick. | Previously given. |
| Inlet Valve Stem Guide. | Worn, stem loose. | Air drawn in on suction thins gas. | Bush guide or use new member. |
| Valve Spring. | Weakened or broken. | Irregular action. | Use new spring. |
| Valve Stem Clearance. | Too little. Too much. | Valve will not shut. Valve opens late, closes early. | Adjust gap .009′′ inlet,.010′′ exhaust. |
| Valve Spring Collar Key. | Broken. | Releases spring. | Replace. |
| Cam. | Worn cam contour. Loose on shaft. Out of time. | Valve lift reduced. Does not lift valve. Valves operate at wrong time. | Previously given. |
| Cam-shaft Bearing. | Looseness or wear. | Valve timing altered. Valve lift decreased. | Replace. |
| Cam-shaft. | Twisted. | Valves out of time. | Previously given. |
| Cam Fastening. | Worn or broken. | Valve action irregular. | Replace with new. |
| Valve Operating Plunger. | Loose in guide. | Alters valve timing. | Replace with new. |
| Valve Plunger Guide. | Wear in bore. Loose on engine base. | Alters valve timing. | Replace or bush. Fasten securely. |
| Timing Gears. | Not properly meshed. Loose on shaft. | Valves out of time. Valves do not operate. | Retime properly. Fasten to shaft. |
| Piston. | Walls scored. | Leakage of gas. | Smooth up if possible. |
| Piston Head. | Carbon deposits. Crack or blowhole (rare). | Cause premature ignition. | Previously given. |
| Piston Rings. | No spring. Loose in grooves. Worn or broken. | Leakage weakens suction. | Previously given. |
| Cylinder Wall. | Scored by wristpin. Scored by lack of oil. | Gas leaks by. Poor suction. | Previously given. |