Knocking or pinking

□ Carbon build-up in combustion chamber. Use of a fuel additive
that will dissolve the adhesive bonding the carbon particles to the
piston crown and chamber is the easiest way to remove the build­
up. Otherwise, the cylinder head will have to be removed and
decarbonised (Chapter 2).

3 Incorrect or poor quality fuel. Old or improper fuel can cause detonation. This causes the pistons to rattle, thus the knocking or pinking sound. Drain the old fuel and always use the recommended grade fuel (Chapter 4).

Z) Spark plug heat range incorrect. Uncontrolled detonation indicates that the plug heat range is too hot. The plug in effect becomes a glow plug, raising cylinder temperatures. Install the proper heat range plug (Chapter 1).

LI Improper air/fuel mixture. This will cause the cylinders to run hot and lead to detonation. Clogged jets or an air leak can cause this imbalance. See Chapter 4.

Piston slap or rattling

□ Cylinder-to-piston clearance excessive. Caused by improper
assembly. Inspect and overhaul top-end parts (Chapter 2).

Fl Connecting rod bent. Caused by over-revving, trying to start a badly flooded engine or from ingesting a foreign object into the combustion chamber. Replace the damaged parts (Chapter 2).

I Piston pin or piston pin bore worn or seized from wear or lack of lubrication. Replace damaged parts (Chapter 2). Piston ring(s) worn, broken or sticking. Overhaul the top-end (Chapter 2).

□ Piston seizure damage. Usually from lack of lubrication or
overheating. Replace the pistons and bore the cylinders, as
necessary (Chapter 2).

D Connecting rod upper or lower end clearance excessive.

Caused by excessive wear or lack of lubrication. Replace worn parts.

Valve noise

I Incorrect valve clearances. Adjust the clearances by referring to

Chapter 1. _ Valve spring broken or weak. Check and replace weak valve

springs (Chapter 2).

□ Camshaft or cylinder head worn or damaged. Lack of lubrication
at high rpm is usually the cause of damage. Insufficient oil or
failure to change the oil at the recommended intervals are the
chief causes. Since there are no replaceable bearings in the head,
the head itself will have to be replaced if there is excessive wear
or damage (Chapter 2).

Other noise

□ Cylinder head gasket leaking.

I ] Exhaust pipe leaking at cylinder head connection. Caused by improper fit of pipe(s) or loose exhaust flange. All exhaust fasteners should be tightened evenly and carefully. Failure to do this will lead to a leak.

□ Crankshaft runout excessive. Caused by a bent crankshaft (from
over-revving) or damage from an upper cylinder component
failure. Can also be attributed to dropping the machine on either of
the crankshaft ends.

I_ Engine mounting bolts loose. Tighten all engine mount bolts

(Chapter 2).

□ Crankshaft bearings worn (Chapter 2).

□ Camshaft drive gear assembly defective. Replace according to the procedure in Chapter 2.

Abnormal driveline noise

Clutch noise

□ Clutch outer drum/friction plate clearance excessive (Chapter 2). U Loose or damaged clutch pressure plate and/or bolts (Chapter 2).

Transmission noise

L Bearings worn. Also includes the possibility that the shafts are worn. Overhaul the transmission (Chapter 2).

I^- Gears worn or chipped (Chapter 2).

Metal chips jammed in gear teeth. Probably pieces from a broken clutch, gear or selector mechanism that were picked up by the gears. This will cause early bearing failure (Chapter 2).

□ Engine oil level too low. Causes a howl from transmission. Also
affects engine power and clutch operation (Chapter 1).

Final drive noise

□ Chain not adjusted properly (Chapter 1).

□ Front or rear sprocket loose. Tighten fasteners (Chapter 6).
Zl Sprockets worn. Replace sprockets (Chapter 6).

Rear sprocket warped. Replace sprockets (Chapter 6). Z) Cush drive dampers worn (Chapter 6).

REF»42 Fault Finding

Date: 2016-01-14; view: 719