FAULT | CAUSE | CURE |
Noisy tappet (with correct clearance) | 1. Wear in rocker pad face and/or rocker sleeve and shaft (OHV). | 1. Reface pad surface, replace rockers or shaft (OHV). |
| 2. Worn cam follower (OHC). | 2. Fit new followers (OHC). |
Lack of compression | 1. Faulty valve seat, excessive wear in stem or guide. | 1. Recut seat and valve, fit new guide and valve. |
| 2. Faulty head gasket. | 2. Fit new gasket or reface head. |
| 3. Worn pistons, rings and bores. | 3. Either fit new rings, pistons and rings and rebore. If engine badly worn then recon. engine. |
Smoke from exhaust. | 1. As above. | 1. As above. |
Lack of power | 2. Blocked crankcase breather. | 2. Check breathing apparatus as above. |
Piston slap | 1. As above (except blocked breather). | 1. As above |
Big-end knock | 1. Wear between big-end shell and crankcase. Wrong torque on bolts. | 1. Depending on wear, fit new shells, regrind crankshaft and check torque. |
Mains rumble | 1. Wear between main bearing shells and crankshaft. | 1. As above. |
Cam follower tap | 1. Camshaft worn or follower dished. | 1. Examine and replace followers or camshaft. Or both. |
Knocking when clutch depressed. Movement at crank pulley | 1. Excessive crankshaft end-float. Wear between crank and thrust washer. | 1. Fit new thrust washers and recheck clearance. |
Clattering from front of engine | 1. Worn or slack timing chain, worn chain tensioner. | 1. Fit new chain and tensioner. Adjust chain where necessary. |
Small-end or gudgeon pin knock | 1. Excessive wear between gudgeon pin and con-rod. | 1. Fit new bush to con-rod. |
Lack of oil pressure | 1. Excessive wear in crankshaft journals. | 1. Overhaul engine. |
| 2. Faulty oil pump. | 2. Fit new pump. |
| 3. Blocked oil pick-up strainer. | 3. Clean pick-up. |
| 4. Faulty pressure-relief valve. | 4. Fit new relief valve. |
| 5. Blocked oil filter. | 5. Fit new filter. |
| 6. Lack of Oil. | 6. Install fresh oil. |
Oil leaks | 1. Sump gaskets or packings. | 1. Fit new gaskets. |
| 2. Front and rear crankshaft oil seal. | 2. Fit new seals. |
| 3. Rocker or camshaft gasket. | 3. Fit new gasket. |
| 4. Oil filter. | 4. Check filter seal. |
Lack of power (engine in good condition) | 1. Faulty ignition timing. Faulty sparking plugs, points or condenser. Wrong valve clearance. | 1. Tune engine. |