Basic Fault Finding
A worn out Battery is the most common fault, its also one of the easiest faults to find and fix (see Battery section below in Electrical Faults).
Basics
Mechanical faults often affect the spark plug.
If the air is restricted you will get a rich mixture,
if the petrol is restricted you will get a lean mixture.
if you get a hole (could look like a crack or slit) in a pipe or rubber which
results in air from outside being sucked in you will also get a lean mixture.
If the mixture is to rich or lean it will ether result in bad engine performance
(and other side effects) or if really bad it will stop the engine from working.
A spark plug colour chart (shows you how the engine has been running, rich /
lean / perfect or other problems).
Look at Normal, Overheated, Carbon Fouled as well as other pictures in the link below.
http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
For more Spark Plug information, see Spark Plug
section below.
Petrol
See Ethanol in Petrol
Warning
Also see Petrol
Petrol ages, if its old petrol it can cause trouble, there are also bad
batches from time to time, try to dilute it with fresh petrol or drain and
replace it.
Some petrol brands and versions have more inbuilt cleaners in than others.
Shell V Power, BP Ultimate, Tesco 99 are more expensive than normal Unleaded
Petrol, but they have extra cleaners in them.
If the engine is able to work, using petrol with extra cleaners in over time
may slowly clean the engine.
Oil
Check the oil level (see Oil page), if its burning oil
the level will drop, you need to see a mechanic if it's substantial.
Make sure you change the oil at the correct mileage or before (see
Oil page).
Spark Plug
Check the spark plug (see owners manual),
look at the colour, this tells you how the engine is running, see
Basics section above for a link to a colour chart.
If its running rich (black sooty deposits = Carbon Fouled) clean the air
filter.
If its running lean check the Exhaust and Silencer (see Exhaust and Silencer
section below), it could also be a fuel starvation (blocked) fault in the
Petrol line.
Its always a good idea to change the spark plug and see if it fixes the fault.
Air filter
Clean it (see owners manual), it's always a good idea to clean the filter and see if it
fixes the fault, this would cause the engine to run rich.
If there are holes in the air filter or if the engine is run without an air
filter, the engine would run lean or not at all. Its very bad for the engine to
run without filtered air.
See Basics section above for more information and links
about rich or lean running.
Exhaust and Silencer
If the Exhaust or Silencer has rusted all the way through it will make the
engine run lean or rich (probably lean).
You must replace it, be careful with non original parts unless it says it will
not change the mixture of the engine (rich / lean).
Clutch or Gearbox
Clutch or Gearbox faults can often be due to Clutch
free play, Chain Tension, Chain Oiling or Idle Speed (check all of these in the
owners manual).
If the clutch has done a very high mileage or has been severely mistreated
over its life and so needs to be replaced,
I very highly recommend you put the EBC brand of clutch plates and clutch
springs in (see Clutch in
General page).
Clutch Cable
Clutch cables break on any motorcycle, often without warning and no way of
predicting it, see Clutch Cable on how to
service and replace it.
Valve Clearance
Check the valve clearance (see Valve Clearance
page).
If the valve clearance is wrong, some of the problems are, engine performance
/ power may reduce, it can make the engine run rich or lean,
reduce compression, hard to start, if its very wrong valve or engine damage may
occur.
If the valve clearance is to big, you may hear excessive noise from the
valves.
If the valve clearance is to small, you may hear no noise from on of the
valves, this is very bad for the engine.
The noise test should not be relied on, you should only rely on the
Valve Clearance page.
Front Disc Brake
If the brake looses pressure or becomes spongy, check fluid level, see
owners manual (also part 12 of
Front Disc Brake fluid
changing)
Brake fluid will become spongy over time, replace it at least every 2 years,
see
Front Disc Brake fluid
changing in Brakes page.
If you hear metal grinding against metal when you use the brake, see Front Disc Brake for new brake pad recommendations.
If the brake seizes on, you need to clean the brake, again its simple, search the internet for information about cleaning.
How to buy and fit a new Battery
How to charge a battery and detect if it is worn out
Light Bulbs
If a light bulb fails, you must fix it as soon as possible, you would fail a
police check and a MOT in the UK.
Never ride in the dark without a working headlight.
Rear Brake light,
if it does not come on when rear brake is applied,
there's an adjustment wire (see owners manual),
Fuses, Connectors, Wires
Check the fuses, (see owners manual),
see if any are blown, there should be spares with them.
If moisture gets in to any electrical connections or wires (usually were the
connectors touch the wire) in the bike, they can corrode (rust),
this increases the resistance for electricity (drops the voltage) and can even
break the connection.
If you have this problem, you need to find it, check any connections you can
find and also look at the wire where it connects to the connector.
If you know how to solder, cutting off the connector and any corroded wire
and soldering instead is much better, it is sealed from moisture and dirt.
Of course if you are bad at soldering, you can create what's known as a dry
joint, this will corrode internally and break the connection.
For people who do not no how to solder, you can do the following.
If the fault is with the wire, you will have to cut off the connector,
cut off all the corroded part of the wire (usually that's only the bit without
plastic around it), take a bit of the plastic off the wire,
then try to reuse the connector or buy a new one.
If the fault is a corroded connector, you can use a normal can of WD40
(available at most motor shops, DIY and even supermarkets).
But only use WD40 if the connector is corroded, WD40 cleans, removes water and
eats corrosion (over time), but leaves a deposit that attracts dirt.
This deposit may help the connection to begin with, but later dirt could brake
the connection,
you can then put more WD40 on and if the corrosion is gone, wipe off the WD40
as much as possible.
On old bikes the electrical wires can become stiff and brittle.
There are several electrical wires that go to the headlight and the front
indicators.
Every time you turn the handlebars these wires are stretched and bent around the
part of the bikes metal frame (chassis) that the handlebars attaches to.
Eventually these wires can brake and even short out, blowing the fuse.
The battery's - (negative = maybe brown or black wire) connector is wired to the
bikes metal frame,
the headlight and front indicator wires are likely to have worn the paint off
the bikes metal frame and so any + wires can short out if there insulation is
worn away.
Some electrical devices on the bike do not have a - (negative wire) instead
they connect to the bikes metal frame to get the - voltage.
When corrosion / rust build up between them it can reduce the voltage or break
the connection.
Battery
Low battery voltage effects all the electrics, including the spark plug.
A test of low voltage is to switch the ignition key on, with the engine off
try the horn, if the tone is much lower than normal, you have low voltage.
You can also do this test with the lights, if they are dimmer than usual with
the engine off, you have low voltage.
If the engine will not start due to low battery voltage and you need it started soon, try switching off the ignition for a minute or two.
If that fails to work you could try bump starting the motorcycle (may or may not
work, depends on your fuel injection, should work with carb models).
I have never bump started (push started) a motorcycle but I believe the
technique is the same for all bikes.
Sit on the bike (I do not recommend you try this off the bike, you could drop
it), switch the ignition on, put bike in to 2nd gear, keep clutch pulled in,
move the bike forwards with your feet as fast as possible (best if its down hill
or get some friends to push you),
let the clutch out smoothly and quickly, when engine starts pull in the clutch.
If that fails to work you may have to open the throttle a bit just before or
when you release the clutch, if that fails you may have to try the bike in 3rd
gear.
To get the bike in to 3rd gear you may need the bike to be moving at the time.
Someone made a video of how to bump start a motorcycle
Motorcycle Bump Start Video
An electric start bike needs a massive amount of power (voltage and
current) to start the engine (battery needs to be healthy and fully charged or
nearly).
A failing battery might seem to have enough voltage but when the electric start
is used the voltage can drop significantly resulting in the engine not firing
up.
The electric start may turn the engine over (might be slower than normal), but
not have enough voltage left to ignite the petrol.
It may not even have enough voltage to turn the engine over and you only hear a
click instead.
If you have a kick-start as well, try it since it needs far less power than an
electric start.
As soon as you take your finger off the electric start button the battery may
return to a good voltage.
My motorcycle automatically cuts off the front headlight
briefly when the electric start is used (this is deliberate design and not a
fault).
Some electric starter motors have failed (they just go click and do
not turn over the engine even though battery is fine),
I believe they fail due to black dust building up inside, all you have to do is
remove the starter motor and clean its insides.
Someone made
a video
Part 1
Part 2
Part 3
Some people have got the starter motor going by hitting it with a hammer
instead.
There is also the possibility that the engine just needs to turn over once or
twice (with ignition off, put bike in to 2nd gear and turn wheel by hand).
There are several reasons for low battery voltage.
1. It's simply worn out, this is by far the most likely.
2. If it's a maintenance battery, so top it up (see owners manual).
3. You have left it for months and so it has gone flat (all bike batteries
loose charge over time so charge it).
4. You have been doing loads of very short journeys and it has not been able
to recharge enough (not so likely if you use a kickstart),
5. The engines battery charger has stopped working or the fuse / wire
connecting it to the battery has failed.
6. You have an alarm fitted and it has drained the battery.
7. You have left the lights on (if your model has that ability).
Testing the motorcycles battery charger is probably easiest by simply
replacing the battery, if the new battery suffers low voltage with use,
it must be the motorcycles battery charger.
You can test the battery with an automatic battery charger, see the section below called How to charge a battery and detect if it is worn out.
You can test the battery, but you could also just replace it.
If you have a voltage meter you can do some basic tests.
When the engine has been off for at least 1-2 hours with ignition key turned
off,
100% Charged 12.60 to 12.8v
75% Charged 12.4v
50% Charged 12.1v
25% Charged 11.9v
0% Charged less than 11.8v
When the engine has been off for at least 1-2 hours,
Switch ignition key on and switch headlight on (engine must not be running),
you need at least 11.5v.
When the engine is running the bikes inbuilt battery charger should raise the
voltage well above 13v especially when the engine revs are well above idling.
You need at least 13.2v to start recharging a 12v battery, only when the voltage
gets close to 14.0v will it be charging well.
Above 14.5v a maintenance free battery will be damaged (voltage can go even
higher if the bikes charging system is faulty).
A maintenance type battery can handle up to 18v, bikes designed to use this sort
of battery often have a charging system that supplies up to 18v.
A failing battery can drag
the bikes inbuilt battery chargers voltage down (also a flat battery will drag
the voltage down far more than a full battery).
But also a failing bikes inbuilt charger can drag the voltage down, increase it
or even fail completely and so not charge the battery at all.
How to buy and fit a
new Battery
When buying a new battery, you need the details of the old one (also see
owners manual).
A new battery will come with an instruction leaflet, if you pour the acid in
to the battery read it,
it will tell you to stand the battery for at least 30 minutes after pouring
the acid in (before charging).
It may tell you to tap the battery to get air bubbles out and pour more acid
in if the level drops on maintenance type batteries.
A new battery is semi charged when assembled (probably 80% charged),
for maximum performance and life it should be fully charged with a charger
before putting it in the bike (see
How to charge a battery and detect its worn out below).
A shop or you can charge it, but it takes time.
After charging for the first time, if it's a maintenance battery the fluid
levels must be checked (ideally pour acid in if needed), see owners manual.
When fitting a maintenance battery, you must connect the plastic breather
tube, it needs to point down and away from the bike,
this is usually in the middle of the bike, just in front of the rear wheel.
This tube may have corrosive gasses and liquids pouring out, so do not let it
point at anything other than the ground.
The battery terminals and any exposed (bare metal, not plastic) metal wires
connecting to them,
need to be protected from the corrosive gasses from the battery, this might
not apply with maintenance free batteries,
but it definitely does for maintenance batteries.
I put any type of grease over them to protect them, you can buy special grease
for this, but there's no need.
Make sure you do not get grease between the battery terminals and the
connectors, unless the grease is designed to allow voltage to pass through it.
How to charge a
battery and detect if it is worn out
Using the correct battery charger is crucial to prevent the battery from being
overcharged and permanently damaged.
Most motorcycle and car batteries are now Maintenance Free type (you must only
use the type your vehicle is designed for),
this means you can not top them up with water (distilled or ionised).
Overcharging boils the battery and water escapes constantly,
as the water level drops in the battery the performance will drop until the
battery becomes useless.
Overcharging happens when the voltage goes above 14.5V.
Overcharging will also happen if voltage is above 13.9V for excessive lengths of
time with a fully charged battery.
That's why most modern battery chargers will ether switch off or drop the
voltage below 14.0V to stop battery from being overcharged.
You must also be careful about the charging current,
to much current and you will overheat the metal plates inside the battery, which
permanently twists and distorts them (severely damaging battery).
A battery is meant to be charged with a current that's 10% of its capacity
(size), for example 4 Ah battery would be 0.4A current.
You can charge at a higher rate but it will harm the battery, 20% is acceptable,
30% is the absolute limit before real damage is expected.
You also have to be careful about modern quality battery chargers which
automatically test the battery to see if it's refusing to charge.
If it thinks it's refusing to charge it will try to force (recover) it with up
to 20V for a short time.
It is crucial if you have one of these chargers that it's designed to work with
your battery capacity (size), the chargers user manual will tell you.
If your battery is below the minimum size the charger will probably think it's
refusing to charge and try to force it with up to 20V every time you put it on
charge.
There are many battery chargers available.
Some have a switch or mode for motorcycles and another for cars (since their
batteries are larger).
Others do not and are designed for ether car or motorcycle batteries only.
It's crucial to choose a battery charger that claims to work with your size of
battery.
It's also important to check it charges up to 14.5V maximum (14.4V and 14.3V are
also ok).
And lastly the charging current (if the charger has a car / motorcycle switch or
mode it's likely to be a higher current in car mode than motorcycle).
I have scene a car / motorcycle charger that supplies 2A current in
motorcycle mode (that's far to much).
Another car / motorcycle charger that only supplies 0.8A current in motorcycle
mode (that ok),
but claims to only work with 7Ah batteries and above, since it has a force
(recover) automatic mode I would not dare use it on batteries below 7Ah.
I have even scene some battery chargers that are so basic they have no fixed
voltage!
Battery Charger well known makes in the motorcycle world (not in any
particular order).
Optimate
Ctek
Oxford
Honda CBF125 and CBR125 use a Maintenance Free 5 Ah battery so ideal charging
current is 0.5A = 500mA (that's 10% of the capacity).
Nearly all Yamaha YBR125 use a Maintenance Free 6 Ah battery so ideal charging
current is 0.6A = 600mA (that's 10% of the capacity)
To charge a battery, you must disconnect at least one of the battery
terminals from the bike.
This is to stop the battery charger damaging the bike's electrical system.
The negative battery terminal is often hooked up to the bikes metal frame, so
its best to remove the positive battery terminal (Red wire),
since if the battery charger accidentally touches the metal frame,
it would send the battery charger voltage through the bikes electrical system
if only the negative terminal was disconnect.
An automatic battery charger will tell you when the battery is fully charged, a faulty or worn out battery will probably never reach fully charged.