Troubleshooting
0-21
7 Cylinder head gasket damaged. If one of the heads is allowed to
become loose, or if excessive carbon build-up on a 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).
8 Stalls after starting
1 Improper choke action. Make sure the choke lever (XV535) or
choke cable (all others) is getting a full stroke and staying in the out
position.
2 Ignition malfunction. See Chapter 4.
3 Carburetor malfunction. See Chapter 3.
4 Fuel contaminated. The fuel can be contaminated with either dirt
or water, or can change chemically if the machine is allowed to sit for
several months or more. Drain the tank and float bowls (Chapter 3).
5 Intake air leak. Check for loose carburetor-to-intake joint
connections, loose or missing vacuum gauge access port cap or hose,
or loose carburetor top (Chapter 3).
6 Engine idle speed incorrect. Turn throttle stop screw until the
engine idles at the specified rpm (Chapter 1).
9 Rough idle
1 Ignition malfunction. See Chapter 4.
2 Idle speed incorrect. See Chapter 1.
3 Carburetors not synchronized. Adjust carburetors with vacuum
gauge or manometer set as described in Chapter 1.
4 Carburetor malfunction. See Chapter 3.
5 Fuel contaminated. The fuel can be contaminated with either dirt
or water, or can change chemically if the machine is allowed to sit for
several months or more. Drain the tank and float bowls (Chapter 3).
6 Intake air leak. Check for loose carburetor-to-intake joint
connections, loose or missing vacuum gauge access port cap or hose,
or loose carburetor top (Chapter 3).
7 Air cleaner clogged. Service or replace air filter element (Chap-
ter 1).
Poor running at low speed
10 Spark weak
1 Battery voltage low. Check and recharge battery (Chapter 8).
2 Spark plug fouled, defective or worn out. Refer to Chapter 1 for
spark plug maintenance.
3 Spark plug cap or high tension wiring defective. Refer to Chapters
1 and 4 for details on the ignition system.
4 Spark plug cap not making contact.
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 Pickup coil(s) defective. See Chapter 4.
8 Ignition coil(s) defective. See Chapter 4.
11 Fuel/air mixture incorrect
1 Pilot screw(s) out of adjustment (Chapters 1 and 3).
2 Pilot jet or air passage clogged. Remove and overhaul the
carburetors (Chapter 3).
3 Air bleed holes clogged. Remove carburetor and blow out all
passages (Chapter 3).
4 Air cleaner clogged, poorly sealed or missing.
5 Air cleaner-to-carburetor boot poorly sealed. Look for cracks,
holes or loose clamps and replace or repair defective parts.
6 Fuel level too high or too low. Adjust the floats (Chapter 3).
7 Fuel tank air vent obstructed. Make sure that the air vent passage
in the filler cap is open.
8 Carburetor intake joints loose. Check for cracks, breaks, tears or
loose clamps or bolts. Repair or replace the rubber boots.
12 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 the 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, lubrication problems). The valves must be
cleaned and/or replaced and the seats serviced if possible (Chapter 2).
13 Poor acceleration
1 Carburetors leaking or dirty. Overhaul the carburetors (Chapter 3).
2 Timing not advancing. The pickup coil(s) or the igniter may be
defective. If so, they must be replaced with new ones, as they can't be
repaired.
3 Carburetors not synchronized. Adjust them with a vacuum gauge
set or manometer (Chapter 1).
4 Engine oil viscosity too high. Using a heavier oil than that
recommended in Chapter 1 can damage the oil pump or lubrication
system and cause drag on the engine.
