The Bullet: Mysteries & Myths
Don't just love but get to know your bullet
- by B. R. Gurunandan
DIAGNOSTIC TESTS YOU SHOULD KNOW
have earlier listed some possible sources of problems. Now here are
some tests that will help to pinpoint the source. The tests are very
simple, and no fancy or costly equipment is called for, but a clear
understanding certainly is ! I have time & again repeated this, and
unashamedly do so yet another time: Systematic process using logic
& common-sense will always work; Blindly using shortcuts and
"expert" advice may land you in a ditch.
Fuel Circuit Tests
One of the most well known tests is the spark-test, where the plug is
removed from the cylinder, resting on the head-fins for earth and the
kick-starter is pressed to see if sparking occurs. Simple ! Only, take
care to observe the strength of the spark, because a weak spark in air
may mean no spark under compression in the engine. If you are not very
comfortable with this, it is a good idea to use a plug with 2mm gap for
the test instead of the normal 0.5mm gap used in the engine so that the
"border-line" components show up. Of course, the test-plug should be
clean and good so there are no doubts about it. If the spark is
missing, feeble or intermittent, then further tests are called for to
pinpoint the cause. Nothing high-tech, they can be all done with
jumper-wires and test-bulb. But we will go into those after discussing
the ignition circuit, and acquiring a clear understanding of it. For
now, go and check out the spark in your engine -when it is running
fine. So it will be easier to judge if the spark is normal when you are
troubleshooting a problem sometime.
Fuel Circuit Tests
Water in fuel, rust/dirt in fuel, blockages in fuel-circuit/jets, wrong
mixture-strength, is a common cause of hard-start, poor-running, or
dying engine. When the spark is OK, one of these is the next suspect.
Fuel-flow: If the bike starts
stuttering after a few seconds at high speeds, you can suspect that the
fuel flow is insufficient.
It may be sufficient at low speeds, but at higher speeds, the higher
consumption is not replenished fast enough, and the level in the carb
keeps reducing until the carb leans out and causes uneven running. If
the bike runs fine at any speed for a while and then stutters at ANY
speed, again starting after a while, then a vacuum-lock is suspect. The
fuel flowing out of the tank causes a vacuum if the tank-vent is
clogged and the gasket is airtight. This reduces the rate of flow,
causing the mentioned problem.
( But, air-tight gaskets ? In a Bullet ? HAAAAAAAAA ! HAHAHAHAHAHAHA ! Yes,
you have rightly gathered that this is a very, very rare case/ cause )
Just pull out the fuel-pipe from the carb and run it into a large
transparent bottle. On turning on the fuel-tap, a healthy flow should
ensue. It should not falter as the bottle is filled.
Slow flow or flow that keeps reducing confirms the above problems
The sources could be clogged tap, clogged filter in tank, or clogged
vent ( Don't rule it out totally !!! ) The remedy is easy. Removing and
reassembling the tap will correct the problem. You don't even have to
drain the tank totally. Tilting the bike ( or tank ) will enable work
with tank almost half-filled. The trouble is not always due to
dirt/ rust. Sometimes the rubber-washer in the tap gets misaligned or
stretched affecting the flow.
Float-Valve: Flooding of the
carb is the symptom. The cause could be dirt/ rust from petrol keeping
the valve open, wear of the valve causing leaks, or punctured float
sinking. Open the float-bowl and look for rust; hold the float up and
turn on the tap to see if there is any flow still; oscillate the float
to check if there is any fuel trapped in it. Usually, it is the
Water in fuel: Misfiring
developing after rain, etc, indicates this. Check out the float bowl of
the carb to confirm. You need not throw away the fuel in the tank.
Drain it into some clean bottles or jerrycan. You can siphon back or decant the
fuel after the water settles. Before that, remove the tank from the
bike and dry it out. The water settles in the bottom, and not all will
be drained through the tap. On running, it will again mix with the fuel
and may land in the carb once more.
Inlet leaks: If the joint
between the carb and head is not airtight, air will be drawn into the
engine thru it, reducing mixture-strength. The effect of this is more
when the throttle is closed, and the volume of air thru carb is less.
( Think about it ! )
Which means that the engine won't start easily, and will not idle
properly, though it may run OK at higher speeds. Reassembling the joint
with new spacer/ gasket and O-ring is a diagnostic + cure, but in an
emergency, you can wrap the joint with a moist rag or smear a sticky
soap all round the edge of the joint, for a temporary cure.
But if you insist on a pure diagnostic, you can dribble some petrol on
the joint as you kick the starter. The petrol ( very ) temporarily seals
the leak - until it gets sucked in. Which enriches the mixture and
starts the engine.
Carb settings: Now this is
not a diagnostic, just very useful advice !
The carb settings are slightly different for each bike, depending on
the characteristics of that particular carb and condition of the
engine. Even if you had it tuned by someone else, it is essential to
know the correct position of the air-screw and idle-screw. Urchins or
idle parking-lot attenders sometimes absent-mindedly scramble these,
and you might have to correct them before the engine will start!
Mixture Strength: This can be
judged from the colour of the spark-plug insulator and electrodes. It
is something you would do in tuning, not troubleshooting, so we'll deal
with it later.
I am sorely tempted to WOW you fellas with accounts of how to use
compression-testers and leak-down testers ! But, heh ! My conscience
would slay me if I bullshitted to Bullet-eers ! The Bullet really does
not call for such gee-whiz technology !
"Dikhaavey Pe Mat Jao; Apni Akal Lagaao" !!! :-)
And, call me a "joroo-ka-gulaam" or a mercenary, but the RoI is much
higher buying a present for your wife than such gizmos for your Bullet.
I call it "Optimization of Resources" :-)
But if you aren't married, hey, go buy a whole bunch of gizmos.
What is, and what is the significance of, the compression test ?
Good compression is one of the requirements of the engine. It implies
lack of leakages from the intake, exhaust or decompression valves, and
past the piston rings. Due to factors like carbon-deposition,
valve/seat-erosion & ring/bore-wear, the leak-tightness of the
engine steadily reduces. This reduces the efficiency of the engine, but
not so much that you could notice too easily.
The compression test of a kick-started single-cylinder is even easier
than the spark test ! We almost do it every time we ( try to ) start it !
OK, to forestall objections, I will qualify that. That's better termed
a compression-check, which just tells you if the leakage is acceptable
We had noted that the Bullet gets by with a surprising amount of
leakage. Of course, leakage is always bad news, but you can usually
live with it till the next convenient overhaul. There are many factors
to this, which is why a precise "psi" value is meaningless for
OK, so how to check the compression of a Bullet engine ?
With the bike on centre-stand and ignition off, operate the
kick-starter ( and decompressor ) till you can feel the resistance of
compression with the k/s lever in approx horizontal position. You
should be able to put plenty of weight on it in this position without
the lever sinking down.
Ideally, a 60kg man should be able to stand on it.
Well, what if he can't ?
What if a 30kg boy makes it sink ? We don't jump to conclusions !
First we check that the decompressor is fully closed by ensuring that
there is a mite of play in its cable. Then twist the valve ( the little
block into which the cable terminates ) back and forth a couple of times
to seat it in case it is being held open by a bit of soot. You can also
hold the decompressor open for a few seconds with the engine running at
speed, to clear the valve and channel of sooty particles. If that was
the cause, the compression will have increased.
If not, we check that the push-rod adjustment ( also called
tappet-adjustment ) is correct.
Well, for the purpose of this test, you should be able to turn the
pushrods freely with your fingers, with the valves closed. How do you
tell that ?
One way is to ensure that the push-rods are in their lowest position.
Press the k/s until they come to their lowest position and stop.
Another way is to press the kickstarter ( with engine decompressed )
until the Ammeter JUST comes back to zero. ( Sparking time; both valves
are closed ) If you still can't turn the push-rods without a spanner,
then they are adjusted too tight. Loosen the locknut and re-adjust them
finger-tight. Did the compression improve ?
No ? Then one of the valves is, or the rings are, leaking.
Well, it could also be a blown head-gasket, but this is easy to see. No
soapy water bubbles required ! The cyl-to-head joint would be messy with
oil in that case. Tighten the head bolts if they are loose, but that
will work only if you are VERY lucky. Usually, a "loose" head-gasket
deteriorates very fast, and needs replacement. Let us assume the joint
Then we are back to valves and rings.
Another "compression test" is in order. This time you need a helper.
First get the k/s lever into horizontal position and feeling max
resistance. Now place a "stopper" such as a jerrycan, or tie a rope to
the k/s lever, etc so that the lever cannot move more than a couple of
inches from the resistance position. Now get the helper to step on the
lever while you listen carefully at the exhaust, the carb ( remove the
hose to air filter ) and the breather-tube in turn.
If the leak is from the exhaust / decompressor valves, you will hear a
hiss at the silencer when the lever is pressed, at carb if the inlet
valve leaks, and breather if rings leak.
Why the stopper??
The idea is to start and end the kick with the valves closed. If the
lever swings more, the exhaust-valve will open and confuse you.
And if the test makes you suspect the rings, you can repeat with 2-5cc
of oil squirted in through the spark-plug hole. This temporarily seals
the rings and you can get more compression to test the other factors.
If the leak is so bad that you cannot easily find the "max resistance"
position, then note that you can still do this test by observing the
position of the push-rods in the "adjustment window" or the ammeter.
How exactly? Hahaha! Read the "back-issues" and figure it out, boys!
Surely some of you are saying, what if the leakage problem is near the
centre of the stroke, not the end?
After all the position of maximum wear IS the centre of the stroke. I
don't say you are wrong. But I would like to mention an offer I made
some years ago. Bring me a Bullet that has severe leak elsewhere, but
perfect sealing near the end of stroke making it impossible to diagnose
by these tests, and I shall repair it free of cost! To this day, I
haven't had the pleasure to thus enhance my experience and knowledge.
But all that was the semi-blind approach, just for the sake of
knowledge. There are some observations from experience or logic, which
will help you to focus your "algorithm" to the most probable areas. If
the problem is sudden, you may not have much to go by. But if it was
slowly building up, the observations over time will tell a story.
Ring/bore wear is to be suspected only in rather aged engines (you
didn't let the oil tank go dry did you!) and if you have been on long,
fast cruises without proper running-in. The decompressor valve is shut
during running, so largely protected from the combustion atmosphere.
The incoming mixture cools the inlet valve. It is the exhaust valve
that is most likely to leak from "burning", especially if your carb is
tuned for economy.
And the symptom is that cold starting is difficult whatever you do.
Bulbs: ( Hey, no snide
comments, please ! We were all newbies once ! )
Here, the trick is to understand the difference between automobile and
household bulbs is in the "connector" or "base". You will see that
whereas in an ( Indian ! ) household-bulb there are two terminals when
there is one filament, there is only one terminal in an auto-bulb with
one filament. The other terminal is the metal-cylinder like in a
torch-bulb. And auto-bulbs like head-lamps, tail-lamps, which have two
filaments have only two terminals! One point is common to the two
filaments and is connected to the metal cyllinder. If you use the two
terminals, you are connecting the two filaments in series, and will
diagnose a good battery as flat, etc!
Also remember that you can't inspect the filament of an auto bulb
visually as you would with a household-bulb, where a broken filament
always sags visibly. Auto-bulb filaments often look OK even when it is
The current they draw is 20 times more for the same wattage, so the
filaments are short and robust, and do not sag if broken. Best test is
by connecting to a battery.
Wiring: Automobile wiring is
extremely elementary on paper, and there is absolutely no difficulty in
figuring out tests for various possibilities. However, the actual
carrying out of these tests is usually not so easy ! The cramped
locations, the necessity of dismantling a lot of things to reach a
particular point, the use of "harness", etc makes it a bit difficult in
The usual problems are some bulb/device not functioning, fuse blowing,
battery discharging. These are the symptoms of frayed/ broken wiring,
shorts and intermittent-shorts respectively. Always start from the
wiring diagram. Locate the problem area on the circuit, and then it is
a matter of simple electrics/ common sense to come up with a lot of
possibilities as to where the wire might be broken or shorting. These
doubts can be resolved by bypassing the suspected segment with a jumper
and observing the change. For shorts, you have to disconnect, not
by-pass, of course.
Here, as usual, visual check is the first thing to do. Most often, the
cause is quite clearly visible! A sharp, limp bend indicates a break of
the conductor inside the insulation; paint rubbed-off at some corner
under the wiring harness indicates chaffing which may be a
potential/intermittent short; broken wires & arcing marks.....but
oh ! We are not in THAT stage any more, right ?
Points: Unless the points are
very drastically spoilt, you can't get consistent results about their
state from milli-volt / milli-ohm readings ! So don't blow your
hard-earned money on a "dwell-meter plus points-condition meter plus
electronic tachometer"; leave that to the "torque-wrench" users !
Hmmmmm…...no prizes now for guessing who sings praises of
electronic-ignition and why !!!
The best way for checking points-condition also is by visual
inspection. The preventive maintenance includes checking that they are
properly aligned, and make contact over the full surface, which should
be free from pits or blue-ing. The points-gap is the least important
parameter ! It controls the dwell, in which there is AMPLE margin in the
Bullet ! If the spark timing is right, just forget about the points-gap !
Capacitor: The capacitor is
easy to check for shorts with a battery and bulb ( it is an
"open-circuit" for DC ), but dielectric-breakdown at higher temp or with
high voltages cannot be tested easily. The capacitor is cheap enough to
test by substitution, but it should be low on your priority list: the
capacitor very rarely fails. Points pitting very soon is an indication
of a dud capacitor, but IF, AND ONLY IF the capacitor-lead and earth
A shorted capacitor results in "no spark", so a simple test is to
disconnect it and see.
Ignition Coil: You can test
the continuity of the primary coil ( +ve to -ve terminals ) and the
secondary coil ( tower-terminal to either of others ) and their
insulation from the casing at room temperature. But you can't test the
internal coil shorting, shorting to case at temp, breakdown of
insulation with temp or atmospheric humidity, etc.
So it makes a lot of sense to simply substitute the coil with a new one
if wiring, points, etc seem OK, but ignition is still not satisfactory.
In fact, it is a great idea to lengthen the coil leads to facilitate
substituting the coil without removing the seat, battery, air-filter,
etc, etc! Or use jumpers………..which you will start to make only when you
REALLY need them ! How do I know ?!
A spare coil is a VERY worthwhile investment, but don't keep it in a
damp/exposed place ! It deteriorates by age & environment almost as
much as by use. So keep the spare sealed in a heavy plastic cover along
with a silica-gel bag, and store it in a cozy place.
Battery: Some very perplexing
symptoms of the electric system can be traced to low acid level in one
or more cell of the Battery! So check this out first. And we assume you
know when to add water and when to add acid, and why.
The things you would like to test the battery for are: Ampere-hour
capacity, and charge-holding capacity. Switching on the headlamp with
the engine off and Battery already fully charged tests the former.
Depending on the size of the Battery and the wattage of your headlamp,
it may be 15minutes to an hour before the lamp dims out with a good
Battery. While a dud Battery will not hold out for more than a few minutes.
Of course, this it is not a scientific way to measure Ampere.hour of
the battery because of unspecified discharge-rate and end-point, it is
just a method to tell if the battery is a dud.
Repeating this test 24 hours after charging fully tells you the extent
of self-discharge of the Battery. If the Battery is still in the bike,
disconnect one of the leads to avoid the possibility of wiring faults
getting diagnosed as Battery fault.
Regulator: This is a
Zener-diode based gizmo that shorts the supply as the voltage
rises above a certain value. Sometimes it is built-in with the
That is a conspiracy ! Because the Regulators blow ten times more
frequently than the Rectifier. So every time your regulator blows, you
get a "Free" Rectifier "bundled-in" !
The test is to measure the battery-voltage with the engine on and
revving to various speeds. The voltage will rise with the revs, from
about 12.4-13.2 to about 14-14.5Volts, not rising any further in spite
of increasing revs. The former is the battery voltage, which depends on
it's state. The latter is the breakdown voltage of the Zener-diode, and
varies with it's mfg-characteristics.
When it is out of the bike, you can test it with a ( bulb and voltmeter
and ) source of variable DC voltage. ( What might happen if there is no
bulb in series during this test ? Hey, don't try it out ! Just imagine
and see ! )
Rectifier: If the regulator
test is OK by battery-charging-test, the Rectifier and Alternator are
OK too ! There are many other ways of testing them, you have to choose
the one that is most suitable to your situation and fits well in your
One is to disconnect the alternator, and connect a 9/ 15 volt ( for 6/ 12
volt battery system, respectively ) transformer in its place. This
"test" can be used to charge the battery too !
Or start the engine in "emergency position" without the battery,
measuring the DC.
Or remove the Rectifier from bike and test it with the multi-meter on
"K-Ohms" range. Or with a "continuity tester" ( a bulb, a cell and
jumpers ! ) The built-in Zener, if any, will not interfere unless it is
shorted. In which case the unit is junk anyway.
Alternator: If the magnet is
not scraping the stator ( you can tell from the noise ), there are only
three things that can ail the alternator: Loss of magnetization of
rotor-magnet, short-circuit or open-circuit of stator-coils. And of
course, the terrible " loose-contact " !
The loss of magnetization is not an overnight phenomenon, and the
symptom is that the charging is less at same RPM than before. So, when
the system is new, or with someone's bike having the same type of
battery & circuit, see the minimum speed at which the Ammeter shows
ZERO with the headlight ( note it's wattage ! ) on, and compare with that
when you suspect the rotor.
An AC voltage on a Digital Multi-meter does not certify the alternator
as good. The high-impedance DMMs record a voltage even by induction ! So
be careful. The real test is the charging of the battery. This rules
out open-circuit ( which allows voltage-induction, but not current-flow )
as well as short-circuits ( voltage will not rise enough to charge the
Note that you should first suspect the regulator, the wiring, the
rectifier, and then finally the alternator. Note also that these
problems are more common in the leads than in the stator-coils
themselves. The short-circuit can occur where the leads go thru the
clutch-case, and the open-circuit at the points where the leads are
soldered to the coils. The loose contacts at the other end of the leads
If by rare chance the stator coils themselves have developed a short or
open-circuit, it is a specialist job. Well, you CAN do it too; also you
can narrow it down to one coil instead of six, but consider this: You
will spend atleast 2-3 days buying the wire, insulation, unwinding,
rewinding, varnishing; whereas you can get a rewound stator in exchange
for your spoilt one plus maybe a 250-300 Rupees, instantly across a
counter ! Moreover, when one coil croaks, others may be having a foot in
the grave already.
The common problems relating to the chassis are: Instability at speed;
wobbling on rough roads; sliding on braking; excessive wear of the
tyres, sprockets, chains; creaks, squeaks, rattles.
They are the result of the following mis-adjustments.
Wheel-Balance: When the tyres
have a heavy-spot, or a gaiter, or run-out makes them non-symmetrical
in terms of weight-distribution, they are "out of balance" and exert
higher forces on the bearings, steering-gear, etc. These forces
increase rapidly with speed, and cause instability, vibration, shudder,
You can easily determine a wheel is out of balance by spinning it
around. As it comes to a halt, an out-of-balance wheel tends to
oscillate, and always stops in the same position, (mark with a chalk or
use the valve-stem as reference) while a normal wheel stops in a
random, different position each time. Note that in case of rear-wheel,
this has to be done when the chain is removed.
Wheel True-ness: When the
spokes are tightened un-systematically or wheel-rim warped, etc, the
tyre runs "out of true" and causes poor grip and faster wear of the
tyre, also contributing to vibration, shudder, etc. Radial run-out will
cause static-imbalance and be seen in above test, but sideways run-out
may not cause appreciable static-imbalance, but yet cause serious
This problem is also detected by spinning the wheel, but with a
reference-pointer to observe sideways out-of-trueness.
Wheel-Bearings: This feels a
very much like a loose steering-head-bearing. You try to rock the wheel
sideways, holding it by the rim at the top and bottom. A bad case will
show perceptible movement on just pulling the rim towards the
swingarm-rod or a fork-tube.
Don't confuse it with loose axles ! Check and tighten them first. You
know how to tighten them now, right ? Or are you still looking for
torque-figure data in Enfield-Manuals ?! :-)
And one more hint: When you open the rear wheel and find the
cush-rubbers sheared, it is a good indication that they have been
trying to compensate for shot bearings.
Loose Steering-head: A very
simple adjustment usually neglected is the steering-head tightness. In
the middle of an "S" bend that can give you a horrible moment, but
worse, it is harsh on the whole steering-gear in the long run. Park the
bike with spacers under the centre-stand, and ask someone to weigh down
the rear-end. Grasp the bottom of the fork, and try to rock it.
Ideally, there should be no relative movement between the bike and
fork. To the extent that if you had a finger on the steering-head
bearing-races, you would still not know someone was rocking the fork.
But if you have not done this test for a long, long time, then you may
be able to feel some movement just by gripping the hand-brake hard and
rocking the bike forward and back when you are astride.
You felt it ? Ooooh ! It's REALLY high time to tighten the head-bearing!
Swing-arm Bush: Finally we
come to the mechanic's favourite ! But take it from me, it is the last
on the probability list. By now you know better than to question
Nandan, of course :-), but the repeated brain-washing by mechanics is a
bit difficult to overcome, right ?
No fear. Consider the facts:
First the Economics !
The wheel-bearings are changed by the mechanic's apprentice in front of
your eyes, and the cost of the bearing is printed on it's box. Whereas,
the bushes are bought on the way to the press-shop and fitted there by
"hydraulic-press", pronounced "God's Abode" and means "justifiably
costs the earth". You meet neither the seller nor installer of the
bushes. Worse, a wipe with a damp cloth, and you can't recognize old
bushes from "new". So if you were the mechanic, would you change the
bushes or the bearings or both ?
Then the Tech !
The wheel-bearings are assembled from about a dozen parts, which move
relatively whenever the bike moves. Whenever you remove the wheel at
the "puncture-repair" shop or on the road, generous quantities of dirt
( grinding paste ! ) enter. You conveniently forget the big chore of
greasing this bearing every 10,000 kms because it is so inaccessible.
It's whine of protest is drowned out by other noises.
A swing-arm-bush is a single piece: Two telescoped steel tubes with
rubber-bonding between them. No crevices for dirt to enter, no
continuous relative movement. Never dismantled for any reason.
NOW you decide.
And I will go to diagnosis. After a bit more of background: Low speed
rear-wobble on rough/ uneven roads indicates slack axle, shot bearing,
or, lastly spoilt bushes. Park the bike with spacers under the center-stand, and try to rock the rear-wheel by grasping it firmly the
tyre. Observe carefully where the movement occurs: At the axle-nuts
( shame! but lucky you ! ) or hub ( 90% probability ! ) or swing arm.
Sometimes the swingarm bush takes much more pressure to budge ! If axle
and bearing are OK, tug the swingarm strongly sideways ( Hey ! Careful !
Have someone hold the bike to prevent it falling on you ! ) If it moves,
yes, it needs attention ! Also note that swingarm bushes fail within a
1000km of installing or above 100000km. Not in between. ( Why ? )
Missing Studs: Shudders,
rattles, knocks during acceleration and deceleration are often due to
loose or missing engine-mounting-studs or head-steady-stud. This is
again a eye-and-spanner exercise.
Wheel-Alignment: You may be
able to ride with wheels badly out of alignment, but the bike will be
badly unstable during emergency braking. And the tyres, chain,
sprockets will have a shorter life.
So sorry if you were expecting me to say the wheel-alignment is tested
with xenon-krypton-laser and dedicated super-computer, it's done with a
length of sewing thread! But more about that in the next session.
Sprockets Alignment: Ideally,
aligning the wheels should take care of this automatically, but
sometimes it doesn't. As there is no provision for easy adjustments to
chain/ sprocket alignment, most people tend to avoid thinking about it!
But how to recognize a misaligned sprocket when it occurs ?
Well, from examining a battered woman you can't say what her husband
drinks, but you can certainly say he needs attention. Likewise, the
chain gives you some indications of sprocket problems, but little more.
It is the sprocket-teeth that tell the tale. Specifically, the SIDES of
the teeth. One side worn more than the other is a dead give-away. But
the full story is obtained on checking the other sprocket also.
More wear on the OPPOSITE side in the other sprocket tells you that the
sprockets are not in the same line.
More wear on the SAME side in the other sprocket tells you that their
axes are not parallel.
This can be confirmed with a length of sewing thread, but is a bit more
difficult than checking tyre-alignment. And correcting is more than a
bit more difficult. But for us Bullet-eers ? Huh ! All in a day's work !
By B. R. Gurunandan
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your queries to Nandan.