0-22
Troubleshooting
5 Brakes dragging. Usually caused by debris which has entered the
brake piston sealing boot, or from a warped disc or bent axle. Repair
as necessary (Chapter 6).
Poor running or no power at high speed
14 Firing incorrect
1 Air filter restricted. Clean or replace filter (Chapter 1).
2 Spark plug fouled, defective or worn out. See Chapter 1 for spark
plug maintenance.
3 Spark plug cap or secondary (HT) wiring defective. See Chapters
1 and 4 for details of the ignition system.
4 Spark plug cap not in good contact. See Chapter 4.
5 Incorrect spark plug. Wrong type, heat range or cap configu-
ration. Check and install correct plugs listed in Chapter 1. A cold plug
or one with a recessed firing electrode will not operate at low speeds
without fouling.
6 Igniter defective. See Chapter 4.
7 Ignition coil(s) defective. See Chapter 4. ,
15 Fuel/air mixture incorrect
1 Main jet clogged. Dirt, water or other contaminants can clog the
main jets. Clean the fuel tap filter, the float bowl area, and the jets and
carburetor orifices (Chapter 3).
2 Main jet wrong size. The standard jetting is for sea level
atmospheric pressure and oxygen content.
3 Throttle shaft-to-carburetor body clearance excessive. Refer to
Chapter 3 for inspection and part replacement procedures.
4 Air bleed holes clogged. Remove and overhaul carburetors
(Chapter 3).
5 Air cleaner clogged, poorly sealed, or missing.
6 Air cleaner-to-carburetor boot poorly sealed. Look for cracks,
holes or loose clamps, and replace or repair defective parts.
7 Fuel level too high or too low. Adjust the float(s) (Chapter 3).
8 Fuel tank air vent obstructed. Make sure the air vent passage in
the filler cap is open.
9 Carburetor intake joints loose. Check for cracks, breaks, tears or
loose clamps or bolts. Repair or replace the rubber boots (Chapter 3).
10 Fuel tap clogged. Remove the tap and clean it (Chapter 1).
11 Fuel line clogged. Pull the fuel line loose and carefully blow
through it.
16 Compression low
1 Spark plug loose. Remove the plug and inspect the threads.
Reinstall and tighten to the specified torque (Chapter 1).
2 Cylinder head not sufficiently tightened down. If a cylinder head is
suspected of being loose, then there's a chance that the gasket and
head are damaged if the problem has persisted for any length of time.
The head nuts and bolts should be tightened to the proper torque in
the correct Sequence (Chapter 2).
3 Improper valve clearance. This means that the valve is not closing
completely and compression pressure is leaking past the valve. Check
and adjust the valve clearances (Chapter 1).
4 Cylinder and/or piston worn. Excessive wear will cause
compression pressure to leak past the rings. This is usually
accompanied by worn rings as well. A top end overhaul is necessary
(Chapter 2).
5 Piston rings worn, weak, broken, or sticking. Broken or sticking
piston rings usually indicate a lubrication or carburetion problem that
causes excess carbon deposits or seizures to form on the pistons and
rings. Top end overhaul is necessary (Chapter 2).
6 Piston ring-to-groove clearance excessive. This is caused by
excessive wear of the piston ring lands. Piston replacement is
necessary (Chapter 2).
7 Cylinder head gasket damaged. If a head is allowed to become
loose, or if excessive carbon build-up on the piston crown and
combustion chamber causes extremely high compression, the head
gasket may leak. Retorquing the head is not always sufficient to
restore the seal, so gasket replacement is necessary (Chapter 2).
8 Cylinder head warped. This is caused by overheating or
improperly tightened head nuts and bolts. Machine shop resurfacing or
head replacement is necessary (Chapter 2).
9 Valve spring broken or weak. Caused by component failure or
wear; the spring(s) must be replaced (Chapter 2).
10 Valve not seating properly. This is caused by a bent valve (from
over-revving or improper valve adjustment), burned valve or seat
(improper carburetion) or an accumulation of carbon deposits on the
seat (from carburetion or lubrication problems). The valves must be
cleaned and/or replaced and the seats serviced if possible (Chapter 2).
17 Knocking or pinging
1 Carbon build-up in combustion chamber. Use of a fuel additive
that will dissolve the adhesive bonding the carbon particles to the
crown and chamber is the easiest way to remove the build-up.
Otherwise, the cylinder head will have to be removed and
decarbonized (Chapter 2).
2 Incorrect or poor quality fuel. Old or improper grades of fuel can
cause detonation. This causes the piston to rattle, thus the knocking or
pinging sound. Drain old fuel and always use the recommended fuel
grade.
3 Spark plug heat range incorrect. Uncontrolled detonation
indicates 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).
4 Improper air/fuel mixture. This will cause the cylinder to run hot,
which leads to detonation. Clogged jets or an air leak can cause this
imbalance. See Chapter 3.
18 Miscellaneous causes
1 Throttle valve doesn't open fully. Adjust the cable slack (Chap-
ter 1).
2 Clutch slipping. May be caused by a cable that is improperly
adjusted or loose or worn clutch components. Refer to Chapter 2 for
cable replacement and clutch overhaul procedures.
3 Timing not advancing.
4 Engine oil viscosity too high. Using a heavier oil than the one
recommended in Chapter 1 can damage the oil pump or lubrication
system and cause drag on the engine.
5 Brakes dragging. Usually caused by debris which has entered the
brake piston sealing boot, or from a warped disc or bent axle. Repair
as necessary.
Overheating
19 Engine overheats
1 Engine oil level low. Check and add oil (Chapter 1).
2 Wrong type of oil. If you're not sure what type of oil is in the
engine, drain it and fill with the correct type (Chapter 1).
3 Air leak at carburetor intake joints. Check and tighten or replace
as necessary (Chapter 3).
4 Fuel level low. Check and adjust if necessary (Chapter 3).
5 Worn oil pump or clogged oil passages. Replace pump or clean
passages as necessary.
6 Clogged external oil lines (if equipped). Remove and check for
foreign material (see Chapter 2).
7 Carbon build-up in combustion chambers. Use of a fuel additive
