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 compression1. 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 power2. Blocked crankcase breather.2. Check breathing apparatus as above.
Piston slap1. As above (except blocked breather).1. As above
Big-end knock1. Wear between big-end shell and crankcase. Wrong torque on bolts.1. Depending on wear, fit new shells, regrind crankshaft and check torque.
Mains rumble1. Wear between main bearing shells and crankshaft.1. As above.
Cam follower tap1. Camshaft worn or follower dished.1. Examine and replace followers or camshaft. Or both.
Knocking when clutch depressed. Movement at crank pulley1. Excessive crankshaft end-float. Wear between crank and thrust washer.1. Fit new thrust washers and recheck clearance.
Clattering from front of engine1. Worn or slack timing chain, worn chain tensioner.1. Fit new chain and tensioner. Adjust chain where necessary.
Small-end or gudgeon pin knock1. Excessive wear between gudgeon pin and con-rod.1. Fit new bush to con-rod.
Lack of oil pressure1. 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 leaks1. 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.