Servicing
Remove the spark plug cap on top of the spark plug
(just
pull it off with a slight twist).
Remove the spark plug with the tools in the bike
(see
How to
find your bikes Tool Kit and Owners Manual in the
Servicing page).
If you have no tools,
you need a 18 mm spark plug tool
that's long enough to go over the top of the plug and reach the nut (a 18 mm
spark plug tool for cars are often to short).
If it's to tight
to turn,
take the bike for a ride to get it up to heat or if it's already
hot, try it stone cold.
Screw a new plug in hand tight (with no tools), then put
the spark plug tool on and tighten it 1/2 a turn.
If you fit a used spark plug, hand tight (with no tools) then put the spark plug
tool on and tighten 1/8 to 1/4 turn.
A turn is 360 degrees.
Put spark plug cap back on (just push on with a slight
twist).
Which Spark Plug
Model
Even if you know which model you need, see the
Important Spark Plug Information
section below.
When purchasing a new spark plug, there are 2 different
models of spark plug for 2 different designs of Honda CG125 engine.
Lots of people and some mechanics can easily make a mistake
since it's often very hard to work out which one you need.
If you have the Owner's Manual, it should tell you.
If you have the original spark plug put in the bike when
manufactured you will know the correct spark plug model.
But shop / mechanics often use spark plug manufacturers
recommendations for Honda CG125 and they are often wrong or misread.
The Haynes Workshop manual is also often used and misread
(very easy to do).
Sometimes a 2nd hand Honda CG125 has its engine changed for the other design
part way through its life.
Check the engine serial number against one of the websites in
Spare Parts section in the
Links page to find the correct spark plug.
The two different spark plug
models are
NGK DR8ES-L
NGK DPR8EA-9
NGK is the name of the manufacture and the rest is their
part number.
Different spark plug manufacturers make equivalent spark
plugs but have different part numbers.
The spark plug manufacturers do have conversion charts so
you can convert from one make to another.
NGK is regarded by most people as the best and Honda
fit them as standard to the Honda CG125.
As a guide, the older the bike, the more likely it will use
the first spark plug model above.
The newer the bike, the more likely it will use the second
spark plug model above.
If you can find your Honda CG125 model number and give it
to a Honda dealer, they should also be able to work out which spark plug you need.
But don't let them simply go by the year the bike was
built, only the model number will give the correct plug.
That's because Honda CG125 are built in several different
country's, one country could make new models and another could always stay
making old models.
Spark Plugs based on year in the UK for example will assume
you have a model imported by Honda UK,
but loads of Honda CG125 in the UK are not imported by Honda UK and
are often old model designs (often a 4 speed gearbox and old
fashioned bodywork).
You might be able to find your model number on the chassis near or behind the
left hand side panel, otherwise you need to find the frame
number,
the Haynes Workshop manual or a Honda dealer may be able to
convert the frame number in to a model number.
Important
Spark Plug Information
If you need a NGK DR8ES-L spark plug (see
Which Spark Plug Model above to find out), you need to set the
gap (search the internet) to 0.7mm yourself.
All of the information below only applies if your engine
uses the NGK DPR8EA-9
The book tells you to clean and check the gap of the plug
every 2500 miles and replace every 5000.
You do not need to check the gap of a new
spark plug,
since its preset at the plug factory to the correct gap
(NGK brand is for sure and is set to 0.9mm, thats what the -9 means at the end
of the model number).
I could not be bothered to clean and check the plug gap at
2500 miles since a new plug only costs £2.99 to £5 dependant on shop.
That means at 2500 miles the plug is only worth £1.50 to
£2.50 so not worth the work of cleaning and checking the gap, so I put a new one
in.
I have been told that cleaning spark plugs can go wrong, you ether do not clean
it well enough or may even damage it.
Its also probably a good idea to change a spark plug every year even if you do
not do the mileage.
You need a NGK DPR8EA-9 spark plug for normal riding and a NGK
DPR9EA-9 for extended high speed riding,
The extended high speed riding spark plug is stated in the
Honda CG125 Front Disc brake models Owner's Manual,
but can not be totally sure for other models, but it makes
sense since its the same spark plug but gets rid of more heat out of the engine.
The following spark plug information is for the front disc
brake model,
I can not be sure if the same would apply to other models.
I found that 54mph in 5th
gear is
high speed for the plug and results in power dropping off if left at that speed
for 1/2 mile.
The power drop off (plug overheating), results in the bike
dropping to 50mph against a very strong head wind, if you slow down allot the
plug will recover.
I fitted the DPR9EA-9 plug and end of problem = no power
drop off and the bikes about 5 mph faster.
If you use the DPR9EA-9 for slow speed (especially idling a lot in traffic jams),
there's a chance the plug will not be hot enough to burn off
petrol burning deposits on the electrode and the bike will stutter or stall.
I have not had any problems, but would not use it if I was
in city traffic all the time with massive amounts of idling,
of course as soon as you get some speed going the plug will
heat up and burn off the deposits.
The petrol quality could also effect this, I use Shell V
Power since it has extra cleaners in it.
You can also buy a NGK Iridium spark plug, I got the one
that's equivalent to the DPR9EA-9,
its made a slight improvement in smoothness, power, pulling power
and less vibration.
Iridium must not be cleaned or the gap changed.
Iridium plugs often cost
3 times more than a standard plug, but will last longer,
I recommend replacing an Iridium every 7,500 miles, that means per mile it works
out at the same cost as a standard plug.
The Iridium plug also claims to burn off deposits more than
a normal plug at slow speeds, so could help the high speed plug potential
problem.
It also claims to require less power from the battery and
ignites the petrol better on cold days.
In the UK, Halfords sell the NGK Iridium plug in their motorcycle section for
£8.99
NGK Iridium Spark Plug Conversion chart
DPR8EA-9 (NGK Normal Plug) = DPR8EIX-9 (NGK Iridium Plug)
DPR9EA-9 (NGK Normal Plug) = DPR9EIX-9 (NGK Iridium Plug)
Servicing
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