TROUBLE SHOOTING
Paragraph
Introduction 28
Engine 29
Engine lubricating system 30
Fuel system 31
Ignition system 32
Generating system 33
Electrical system 34
Transmission and clutch 35
Wheels and chains 36
Brakes 37
Steering 38
28. INTRODUCTION.
=a.= Trouble shooting for the entire vehicle is given in this section.
The engine trouble shooting paragraph traces trouble to a system
affecting engine performance: for example, fuel or ignition. To
trace trouble to one or more defective components of a system, it is
necessary to refer to the pertinent paragraph of this section when the
defective system or systems have been located in the engine trouble
shooting paragraph.
=b.= The material given in this section applies to the operation of the
vehicle under normal conditions. If extreme conditions of temperature
occur, it is assumed the operator of the vehicle has prepared his
vehicle for use for the conditions encountered.
29. ENGINE.
=a. Instruction.= This subparagraph traces troubles to a system
affecting engine performance. Step b below gives simple engine tests
to determine the mechanical condition of the engine. References in
step b refer to step c for engine mechanical troubles, or to pertinent
paragraphs in this section for system troubles, or when a test
indicates a special unit is faulty, to the pertinent paragraph in this
manual.
(1) ENGINE DOES NOT TURN OVER WHEN FOOT STARTER IS OPERATED.
(_a_) Clutch slipping. Check adjustment (par. 48).
(_b_) Sheared engine sprocket key. Replace (par. 65).
(_c_) Starter clutch stuck by congealed oil. Free starter clutch. Use
proper grade of oil.
(_d_) Starter clutch worn. Refer to maintenance personnel.
(_e_) Engine locked (seized). Refer to organization mechanic.
(2) ENGINE TURNS OVER WHEN CRANKED BUT DOES NOT START.
(_a_) Fuel supply valve closed. Open valve.
(_b_) Empty fuel tank. Fill tank.
(_c_) Fuel system faulty. Refer to paragraph 31.
(_d_) Ignition system faulty. Refer to paragraph 32.
(_e_) Battery weak or dead. Refer to paragraph 34.
(_f_) Insufficient compression. Refer to step b, below.
(3) WEAK COMPRESSION. Refer to step b below for test.
(_a_) Improper valve tappet adjustment. Adjust (par. 43).
(_b_) Valves sticking. Use dry‐cleaning solvent to free valve stems in
guides.
(_c_) Faulty lubrication. Refer to paragraph 20.
(_d_) Loose cylinder head bolts and/or faulty gasket. Tighten head
bolts or replace gasket (par. 41).
(4) OVERHEATING.
(_a_) Faulty fuel system. Refer to paragraph 31.
(_b_) Dirt on cylinders. Clean fins on cylinder, especially the fins on
cylinder head.
(_c_) Defective lubrication system. Refer to paragraph 30.
(_d_) Defective ignition system. Refer to paragraph 32.
(_e_) Idling engine without having vehicle in motion. Do not idle
engine longer than 1 minute.
(_f_) Valve tappet adjustment incorrect. Refer to step b (1) below for
test, to paragraph 43 for adjustment.
(_g_) Drive chains too tight. Adjust (pars. 59 and 60).
(_h_) Excessive carbon deposits. Refer to organization mechanic.
(5) LACK OF POWER.
(_a_) Defective fuel system. Refer to paragraph 31.
(_b_) Defective ignition system. Refer to paragraph 32.
(_c_) Overheating. Refer to step (4) above.
(_d_) Defective lubricating system. Refer to paragraph 30.
(_e_) Poor compression. Refer to step (3) above.
(_f_) Drive chains too tight. Adjust (pars. 59 and 60).
(_g_) Brakes dragging. Adjust (pars. 96 and 97).
(6) POPPING AND SPITTING THROUGH CARBURETOR.
(_a_) Water in fuel. Water may be present in fuel tank and carburetor.
Drain and refill fuel tank and carburetor bowl.
(_b_) Incorrect valve tappet adjustment or sticky valves. Test (step
=b= (1) below). Adjust tappets (par. 43). (_c_) Defective ignition
system. Refer to paragraph 32.
(_d_) Defective fuel system. Refer to paragraph 31.
(_e_) Weak and/or broken valve springs. Refer to higher authority.
(7) SPARK KNOCK.
(_a_) Defective ignition system. Refer to paragraph 32.
(_b_) Excessive carbon deposits. Refer to step b (2) below.
(_c_) Defective fuel system. Refer to paragraph 31.
(_d_) Defective lubrication system. Refer to paragraph 30.
(8) POUNDING AND EXCESSIVE METALLIC NOISE.
(_a_) Front drive chain too loose. Refer to paragraph 36.
(_b_) Engine sprocket loose on shaft.
(_c_) Excessively loose valve tappets. Adjust (par. 43).
(_d_) Engine mounting bolts loose. Tighten.
(_e_) Transmission mounting stud nuts loose. Tighten (par. 60).
(_f_) Spark timing incorrect. Adjust.
(_g_) Internal parts of engine worn or broken. Notify organization
mechanic.
=b. Tests to Determine Mechanical Condition of Engine.=
(1) RINGS AND VALVES. This is a simple compression test. If possible,
make this test with the engine warm. Ignition switch must be off. Crank
engine slowly, placing entire weight of body on starter crank. Engine
compression should sustain the weight of an average size rider several
seconds before crank passes through complete range of its travel. If
engine offers little resistance to starter crank in testing either or
both cylinders, it is an indication that compression is not adequate in
one or both cylinders. No clearance or insufficient clearance at valve
tappets; valves sticking in guides; valves seating poorly; cylinder
heads leaking; spark plugs loose in heads; piston rings badly worn
and/or broken; cylinder and pistons badly worn, or lack of lubrication
could cause the above condition. Make external checks first: See that
oil is in tank, that spark plugs are tight, and examine around cylinder
heads for signs of leaking oil deposits. In extremely cold weather,
resistance to the starter crank is increased by “stiff” oil in engine
and transmission. Therefore, do not mistake this condition to indicate
actual engine compression.
(2) ABNORMAL ENGINE NOISE. Owing to constructional design of the
motorcycle, correct adjustment of the several units and components
is necessary for smooth and normally quiet engine operation. Many
motorcycles have been “deadlined” and engines exchanged because
simple tune‐up service and correct adjustment of components have been
neglected. Rough, jerky, and noisy engine action at low speed riding
is usually caused by excessively loose front and rear drive chains,
or by a transmission being loose in its frame mounting. Fast idling
of engine with the front drive chain too loose, may give the false
impression that the engine bearings and pistons need replacement
service. Engine sprocket loose on its shaft will cause a pounding noise
similar to that of badly worn engine bearings. If front drive chain
is too tight, or engine sprocket and chain are badly worn, a grinding
noise results, seeming to come from the engine. Excessively loose valve
tappets will cause abnormal metallic noise in the valve timing gear
train and engine crankcase. Spark advanced too far will cause rough
engine performance at low speeds as well as spark knock, pounding,
and overheating. Engine pounding and rough operation with consequent
noise, result from loose mounting bolts. Generator mounted to give
insufficient gear‐tooth clearance will cause “howl” in gear case.
30. ENGINE LUBRICATING SYSTEM.
=a.= Action of the oil feed pump is indicated by the red signal light
located in right side of instrument panel. (Red signal light is
normally grounded by the oil pressure switch. When oil pump pressure
is built up several pounds, diaphragm opens the signal light circuit.)
Action of the scavenger (oil return) pump is indicated (engine running)
by oil dripping from 1/8-inch hole in oil return tube (large tube)
inside oil tank, just back of oil gage rod (dip stick) tube. Since
the oil feed pump and scavenger pump are separate units, operated
individually, it is possible (due to faulty unit) for either to
function alone, thus affecting engine oil pressure and return of oil
to the tank. Action of the vent pipe (small pipe) located within the
oil tank is of a “breather” nature; its function not being indicated in
any manner. Before attempting to diagnose trouble in engine lubricating
system, rider must be familiar with and understand indications by
instrument panel signal lights (par. 7 =f=).
=b. Red Signal Light Fails to Burn When Ignition and Light Switch is
Turned On.=
(1) Check other lights to determine if battery is “up” and that switch
and wiring connections between battery and switch are in good order.
See that wire connection is secure and screw is tight on oil pressure
switch terminal. Failure of light to burn after these checks indicates
that either the lamp is burned out or oil pressure switch is faulty.
(2) Test to eliminate the oil pressure switch by removing wire from
switch terminal; ground wire on switch body and note if red light burns
with ignition and light switch in “ON” position. If light burns, it
indicates that oil pressure switch is faulty, and must be replaced.
If light does not burn in making this test, it indicates that lamp is
burned out. Remove panel cover (par. 119) and replace lamp.
=c. Red Signal Light Continues to Burn After Engine Is Operated Above
Idling Speeds.=
(1) Check oil supply in tank. If light fails to go out after engine
is warm, or after 1 minute of operation, further checks must be made
to locate trouble, as indication points to faulty engine lubrication
system, or fault in signal circuit. Eliminate the signal system first.
(2) Test oil pressure signal switch to panel signal light circuit.
Remove wire from oil pressure switch terminal by turning on ignition
and light switch and observing red signal light. If light burns, short
circuit in wiring exists. If light does not burn, it indicates normal
condition, leaving oil pressure switch of the signal circuit to be
tested.
(3) Install new oil pressure switch and start engine. If red signal
light goes out after engine is operated above idling speeds, it
indicates trouble in oil pressure signal switch. If red signal light
continues to burn, it indicates trouble in oil feed pump. Replace pump
(par. 44).
=d. Excessive Smoke Issues from Exhaust and Oil Spray Issues from
Gear Case Breather Outlet.= This is an indication that the scavenger
pump is not draining engine crankcase and returning oil to tank. With
engine running at idle speed, examine oil return in tank. Remove tank
oil cap, and with a small flashlight (tactical situation permitting),
observe whether or not oil is dripping from 1/8-inch hole in oil return
tube. Hole is on under side of tube and is located just back of oil
gage rod tube. If observation is poor, place finger over hole and
feel for pulsation of oil pressure. If oil does not return to tank,
scavenger pump is faulty. Should the crankcase breather valve be
incorrectly timed, smoke will issue from the exhaust, but not as
noticeably as when scavenger pump is not working. Refer to step e below
for this condition.
=e. Smoke Issues from Exhaust and Excessive Oil Condition Exists Around
Cylinder Exhaust Ports= (=where exhaust pipes enter cylinders=). Engine
scavenger pump and crankcase breather valve are one unit, operated by
worm gear located behind engine shaft pinion gear. Although scavenger
pump is not “timed,” the breather valve sleeve which drives it must be
timed to balance the engine lubricating system. If for any reason the
scavenger pump unit is removed from engine base, the breather valve
must be retimed (within the gear case) when pump assembly is replaced.
Incorrectly timed breather valve will force oil past piston rings,
causing some smoke, besides forcing oil out through exhaust ports,
causing excessive oily condition around exhaust pipes where they enter
cylinder ports.
31. FUEL SYSTEM.
=a.= Many symptoms which might be attributed to the air‐fuel system
are, in reality, due to faulty ignition. Before attempting any but the
obviously required adjustments, check the ignition system thoroughly.
Gasoline tank supply valve is a dual purpose valve, and its operation
is explained in paragraph 5 =b=.
=b.= Shut off gasoline supply valve. Disconnect fuel line at strainer,
open valve, and observe free flow of fuel from pipe. If line is
plugged, remove, clean out, and replace.
=c.= Remove, disassemble, clean, and install fuel strainer (par. 72).
=d. Hard Starting, Spitting, and Misfiring Caused by Water in Fuel.=
Remove drain screw from carburetor bowl, drain bowl, and replace screw.
Take care not to cross drain screw threads when replacing. If there is
still evidence of water, dirt, or other foreign matter after bowl is
drained, replace carburetor (pars. 70 and 71). Remove air cleaner oil
cup and inspect for evidence of water in oil. Drain, clean, refill to
correct level mark, and replace cup. Should above procedure fail to
eliminate trouble, drain fuel tank by removing drain plug located under
tank in forward position. Replace drain plug and refill tank with fuel.
=e. Hard Starting, or Missing at Idling and Low Speeds.= Carburetor
low speed circuit in need of adjustment (par. 68). Carburetor high
speed circuit is controlled by a fixed jet.
=f. Impossible to Obtain Satisfactory Carburetor Adjustment: Lean
Spot Between Idling and Up to 30 Miles per Hour Speeds.= Carburetors
in service for some time become dirty and crust forms in the throttle
barrel, making satisfactory low speed adjustment difficult, if not
impossible. Replace carburetor (pars. 70 and 71).
=g. Fuel Leaking from Carburetor.= Evidence of dirt in float valve,
incorrect float level, or faulty float. Replace carburetor (pars. 70
and 71).
=h. Difficult Starting, Fuel Mixture Too Rich.= Air cleaner oil
cup overfilled, or cleaner elements exceptionally dirty, choking off
adequate air supply to carburetor. Check the oil cup level. If oil cup
level is correct, remove, clean, and install cleaner elements (par. 76).
32. IGNITION SYSTEM.
=a.= When checking ignition system for trouble, make the most obvious
and simple checks first. For example: Turn on ignition and light
switch, observe lights to ascertain battery current supply; then check
to see that current is reaching spark coil, circuit breaker, etc.
Faulty spark plugs are responsible for the great majority of engine
ignition troubles. There is no service for spark plugs other than
sandblast cleaning and correct adjustment of electrodes. Questionable
spark plugs must be replaced (par. 83).
=b.= Remedy all poor connections in ignition wiring system (fig. 48).
=c.= Remove circuit breaker cover, operate engine with starter pedal,
and observe opening and closing of circuit breaker points. Correct
point gap when breaker lever fiber is on highest point of cam is 0.022
inch. For adjustment refer to paragraph 84.
=d. Testing for High Tension Spark.= Spark at plug gaps depends
upon condition and operation of circuit breaker points, condition of
condenser, and condition of spark coil and high‐tension cables. Testing
the ignition system is best done by means of elimination, testing
each unit by replacement until trouble is located; then replacing
serviceable units which were removed.
(1) Remove spark plug cable terminal from either plug, leaving other
cable and plug connected (to effect ground return of high‐tension
current); turn engine until circuit breaker points are closed; turn
ignition and light switch on; hold high tension cable terminal 1/4 inch
from cylinder; open and close circuit breaker points with finger and
observe spark jump at gap. If spark jumps gap, it indicates ignition
primary and secondary circuits are complete.
(2) No spark at high‐tension gap calls for testing of primary and
secondary circuits. Turn engine until breaker points are held open;
hold cable end 1/4 inch from cylinder; turn ignition switch on and with
the bit of a screwdriver, make a good ground connection between breaker
movable (lever) point, and the ground. If a good spark is obtained
at high‐tension cable terminal gap when ground connection made by
screwdriver is broken, clean or replace faulty breaker points (par. 84).
(3) If circuit breaker points are in good condition, but no spark (or
a very weak spark) occurs at high‐tension gap, replace condenser (par.
85) and repeat test under step (1) above. If replacement of condenser
does not remedy trouble, replace spark coil (par. 89).
(4) If tests made under steps d (1), (2), and (3) above show ignition
system to be in good order (no units having been replaced), and
ignition trouble still exists, it means that breaker points, condenser,
and spark coil must be replaced with new units and engine road test
made with each replacement until trouble has been located and remedied.
=e. Ignition System Tests Satisfactory but Engine Starts Hard,
Overheats or Misses.= Clearly an indication that spark plugs are
faulty. Remove spark plugs, clean with sandblast, regap points between
0.028 inch to 0.030 inch and reinstall. Replace defective plugs with
new ones of correct (No. 2) heat range (par. 83).
=f. Engine Misses After Warm‐up, or When Quite Hot.= Replacement of
spark plugs should remedy this trouble. If it does not, then either the
condenser or spark coil is at fault. Replace condenser first (par. 85).
If new condenser fails to correct trouble, replace spark coil (par. 89).
33. GENERATING SYSTEM.
=a. Panel Green Signal Light Continues to Burn Above 20 Miles
per Hour.= Correct faulty wiring and connections between battery
and generator. Refer to figure 55. Inspect condition of relay and,
if necessary, replace (par. 95). Inspect brushes and commutator of
generator. Clean commutator if necessary (par. 91). If brushes are
sticking in holders or badly worn, replace generator (pars. 93 and 94).
=b. Generator Output Fails to Keep Battery Charged Although Green
Signal Light Behavior Is Satisfactory.= Test battery: if it will not
hold charge, or is defective, replace (par. 113). If the machine is
used most of the time for night operation, have a higher echelon
increase the generating charging rate. Inspect brushes and commutator
of generator. Clean commutator if necessary (par. 91). If brushes are
badly worn or sticking in holders, replace generator (pars. 93 and 94).
34. ELECTRICAL SYSTEM.
=a. Panel Lamps Do Not Light When Switch Is Turned On.= Examine
each lamp and if burned out, replace (par. 120). Examine battery; if
discharged, replace (par. 113). Remedy defective wiring and connections
(fig. 71). Test light switch: if defective, replace (par. 116). Test
blackout light switch (in lamp body): if defective, replace lamp (par.
114).
=b. Lights Burn Dim but Brighten Up Considerably When Engine Is
Accelerated.= Test battery with hydrometer. If it is not fully charged,
replace (par. 113). Remedy defective wiring, connections, and switches
in circuit (fig. 73). If the battery runs down again after a short
period of operation, have the generator output increased (refer to a
higher echelon).
=c. Lights Exceed Normal Brilliancy When Accelerating Engine.=
Examine battery: if defective, replace (par. 113). Remedy faulty wiring
and connections (fig. 73). Do not forget the ground connection of the
lamp body.
=d. Blackout Stop Lamp and/or Service Stop Lamp Fail to Light.= If
the unit is burned out, replace it (par. 115). If the brake pedal is
not operating switch, remedy the faulty operation. Remedy all faulty
wiring and connections (fig. 73).
=e. Horn Does Not Sound When Ignition and Light Switch Is Turned
On and Horn Button Is Pressed.= Test battery by turning on lights. If
lights are dim, replace battery (par. 113). Remedy defective wiring
and connections (fig. 73). If the horn does not respond to adjustment,
replace (par. 117).
35. TRANSMISSION AND CLUTCH.
=a.= Need for attention to clutch and controls is indicated by clutch
slipping under load or dragging (transmission gears will shift hard and
clash) when in disengaged position. In either case, the first thing to
be checked is adjustment of controls; this being the attention usually
needed. Indication that gear shifter controls are in need of adjustment
is when transmission gears “jump” out of engagement when accelerating
vehicle or when under heavy pull. CAUTION: _This warning must not be
disregarded._
(1) CLUTCH SLIPS WHEN FULLY ENGAGED. Adjust clutch control (par. 48).
Adjust clutch spring tension (par. 48). If the clutch still slips,
replace either the disks, springs, or both (par. 48).
(2) CLUTCH DRAGS WHEN FULLY DISENGAGED. Adjust control (par. 48).
Adjust spring tension (par. 48).
(3) CLUTCH RATTLES WHEN IN DISENGAGED POSITION, ENGINE IDLING. In
this case, the clutch probably was not properly assembled. Refer to
paragraph 51 =a=.
(4) TRANSMISSION “JUMPS” OUT OF GEAR UPON ACCELERATING VEHICLE, OR WHEN
UNDER HEAVY PULL. Adjust shifter lever control linkage (par. 54).
(5) TRANSMISSION GEARS SHIFT HARD OR CLASH WHEN CLUTCH IS FULLY
DISENGAGED. Adjust clutch control linkage and spring tension (par. 48).
Make sure the transmission mounting bolts and units are tight (pars.
57 and 58). Drain and fill transmission with correct lubricant (fig.
10). If the above methods fail to cure the symptom, refer to a higher
authority.
36. WHEELS AND CHAINS.
=a. Transmission Countershaft and Rear Wheel Sprockets Show Excessive
Wear on One Side of Teeth.= Adjust the position of the rear wheel axle
to aline the rear wheel sprocket with the transmission sprocket (par.
60). If they cannot be alined, the frame is out of alinement, and the
trouble must be referred to a higher authority.
=b. Chains Produce Grinding Noise with Engine Idling and Vehicle on
Rear Stand.= If either chain is adjusted too tight, adjust to proper
tension (pars. 59 and 60). Examine both chains for presence of dirt
and grit. If dirty, clean and lubricate them (par. 20 =c= (10)). If
either chain is dry, adjust chain oilers (par. 61). Badly worn chains
and sprockets will cause this symptom; the worn parts must be replaced
(pars. 62 and 63).
=c. Front Chain Dry and/or Red (Rusty) in Appearance.= The chain in
this condition has not been receiving enough lubrication. Adjust chain
oiler (par. 61). If the chain is damaged from lack of oil, replace
(par. 62).
=d. Rough or Jerky Vehicle Operation at Low Speed.= Chains are too
loose. Adjust (pars. 59 and 60).
=e. Excessive Side Play at Rim of Front Wheel.= Adjust bearing cones
(par. 126). If the cones and or hub races are badly worn, replace wheel
(par. 125).
=f. Front Wheel Spinning Test Produces Grinding, Grating Noise (not
in brake).= The wheel bearings are defective. Replace wheel (par. 125).
=g. Rear Wheel Has Excessive Side Play at Rim of Wheel.= The hub
bearings are defective. Replace wheel (par. 127).
=h. Rear Wheel Has Side Play in Excess of 0.010 inch on Axle.= The
thrust washers of hub are worn or damaged. Replace wheel (par. 127).
=i. Rear Wheel Spinning Test Produces Grinding, Grating Noise=
(=chain removed=). Tighten wheel mounting screws. If this does not
correct noise, replace wheel (par. 127).
37. BRAKES.
=a. Rear Brake Does Not Hold When Foot Pedal Is Depressed.= If the
brake linings are wet, operate the vehicle and apply a slight pressure
to the brake pedal to dry out linings. After drying the linings adjust
brake rod length (par. 96 b). If the brake operating lever stands ahead
of the vertical position with brake applied, or the brake does not
hold, replace the defective brake shoes (par. 96).
=b. Rear Brake Squeaks or Chatters When Used.= Tighten side plate
sleeve nut, if it is loose. Adjust shoe position (par. 96). If the
operating camshaft and/or side cover bearing is worn, replace the
assembly (par. 96). If the brake shoe spring is defective, replace
(par. 96). If the lining on the brake shoes is loose, worn, or
defective, replace shoes (par. 96). If the brake drum is worn or
damaged, replace the brake drum and sprocket assembly (par. 96).
=c. Rear Brake Drags (vehicle on rear stand).= Adjust linkage (par.
96). If it still drags, equalize shoe assemblies, and adjust linkage
(par. 96).
=d. Front Brake Does Not Hold When Hand Lever Is Operated.= Adjust
brake control (par. 97). If brakes are wet, operate vehicle a short
distance with slight pressure on brake lever to dry out linings. If
brake does not hold, replace shoes (par. 97).
=e. Front Brake Drags.= Adjust control linkage (par. 97). If brake
still drags, equalize shoes and readjust control linkage (par. 97).
=f. Front Brake Action Rough and/or Chatters.= Adjust control linkage
assembly (par. 97). If malfunction continues, examine brake shoes,
shoe spring, camshaft bearing and side cover bearing. Replace any
defective parts or assemblies (par. 97).
38. STEERING.
=a. Motorcycle Pulls to One Side.= Inspect and correct alinement of
rear wheel (par. 60). If the front forks are bent or twisted, replace
(par. 98). If trouble persists, refer to higher authority.
=b. Motorcycle Weaves from Side to Side.= Adjust steering damper to
suit speed and road conditions. If this fails, inflate tires to correct
pressure. Make sure rear wheel mounting screws are tight. If the
steering head bearings are too tight, weaving will result. Check the
steering head bearings (par. 98), and adjust if necessary.
=c. Motorcycle Shimmies at High Speed.= Inflate tires to correct
pressure. Adjust steering damper to suit speed and road conditions. If
the tire tread is unevenly worn, and shifting tires does not correct
the condition, replace the defective casings. Make sure the axle nuts
are tight. If the rocker plate studs and bushings are badly worn, or
the fork springs are broken, replace (par. 98).