Motorcycle Owners Club

Honda CG125 but also some universal motorcycle information

Honda CG125 General

How to Clean a Motorcycle

Never use a pressure washer to clean any motorcycle, water can get in to wheel bearings and in to the electrical system.
I have never needed to use any detergent or shampoo on a motorcycle (I just use water).
At least one motorcycle manufacturer advises you not to use washing up liquid since it contains salt that will scratch paintwork.
I use on paintwork, chrome and glass
a General Microfiber Cleaning Cloth (often sold for normal house cleaning),
which is very good at removing grease, dirt and insects, but is not the best finish.
I also use a Genuine Chamois Wash Leather (available from car shops, do not get the artificial type),
which is not good at removing grease, dirt or insects but leaves a smear free finish.
A Spectacle / Camera Microfiber Cleaning Cloth (used to clean mirrors, instruments and helmet visors), is good at everything.

I also use Mer Car polish
(every 6 months to 2 years on the paintwork to make it really shine and make it slippery so insects do not stick like glue).
Mer Car polish is expensive but you use hardly any on a motorcycle so the smallest bottle will last almost forever.
I also use it on the Silencer / Exhaust and it can be used on any of the chrome on the bike (I have never bothered).
See Silencer / Exhaust section only in Bike part of Riding In Winter page to see how to remove rust and stop rust coming back.

If I need a strong degreaser to remove for instants months of chain oil from the back wheel,
I would use WD40 (only because I having it around anyway) and an old cloth.
WD40 is a very powerful degreaser and flows like water in to all the very small places,
this is very bad if it gets in to the wheel bearings and other places
since it will get past the rubber seals and dissolve the bearing grease.
So spray only a small amount on to the back wheel and rub with a cloth,
it often leaves a WD40 film of oil afterwards, do not let it get on the silencer or it will stain.
I normally do not bother to remove the chain oil from the back wheel since it protects the wheel and prevents rust.

Gear Change Lever

You can adjust the Gear Change Lever height to the size of your boots or shoes.

The motorcycle dealers often set it pointing down,
which is totally wrong for a Honda CG125 since the riding position is upright not forward.

The Owner's Manual shows the gear change lever at the same height as the foot rest (level with the foot rest).
I found this to be correct for my boots and expect it to be the same for most people.

To adjust the gear change lever,
remove the nut bolt (10 mm),
take the lever off the bike,
put it back on in the correct position,
put the nut bolt back in,
(if you do not put the gear lever back far enough
or to far back, the bolt will not go through).

Rear Suspension

Adjust the Suspension to the weight you are carrying.
There are probably 5 settings on each side of the bike.
Make sure both are on the same setting.

You can adjust it by turning the bottom of the suspension around.
You may be able to turn it with your hands if you are strong enough,
if not use the C spanner (may need the extension shaft),
see How to find your bikes Tool Kit and Owners Manual in the Servicing page.

When the suspension is new,
the lowest setting (opposite to stiff) is not normally used since it's for light people with smooth roads.
The standard setting is the one above the lowest setting.
The maximum setting (stiffest) is for carrying a passenger.

The correct suspension setting for you will depend on your weight and how old / worn the suspension is;
all springs age / wear and drop in stiffness.
It's simply a matter of trial and error, it will affect how well the bike handles round bends and handles bumps in the road.

How to stop your engine from clogging up

It's a good idea with any engine, if it's only been on short trips, like 5 miles to work,
to take the bike for a long fast ride to clean it out.

Any engine that does not get up to full temperature (low engine revs or short trips)
will get condensation inside and burning deposits will build up excessively,
that's why you have to change the oil more often in these cases,
but you still need to take the bike out for a long fast ride from time to time, it can also help the chain.

Lots of people think the Honda CG125 has a small engine,
so it will get up to full temperature very quickly
and its engine speeds are much higher in normal operation than larger engines.

Well the temperature takes a lot longer than many think, 5 miles just does not get it up to full heat.
I have noticed that if you do loads of 5 mile trips at 40mph in 5th gear the bike suffers.

But when you take it out for a 50mph or faster run,
of at least 15 miles it cleans itself out (you still need to change the oil more frequently).

You may notice the bike starts better; idling is faster and healthier, less vibration, smoother and more power.

If you do a lot of short, slow trips try to have a long fast one now and again.

You can also buy better quality petrol that has extra cleaners in to reduce the problem (see Petrol below).


The choke lever is underneath the left hand side of the petrol tank.
When the lever is up (position a) the choke is on and down (position b) it's off.

A few of the Front Drum brake models have reversed the choke lever so down is on and up is off.

The Choke on some Front Drum brake models may not be needed in summer (when the outside air is hot).

The following is for the Front Disc brake model,
some of it may be true for Front Drum brake models (not all of it since their emission controls are not so strict).

As long as you have the Idle Mixture Screw and Idle Speed Screw set right (see Idle Screws page) all the following is true.

Half choke is never any real use; bike still needs full choke on a hot summer's day.
The bike has a very small window of when half choke works like 2 seconds or never.
Never leave the choke half on when the engine does not need choke,
over time it will damage the engine, the bike will not stall when idling with half choke.

Full choke is not strong enough when engine is stone cold in the middle of winter;
you have to generate heat by turning the engine over a few times,
below 10c a small heater is also activated to help.

To start the bike from stone cold, put choke fully on.
Open the throttle 1/8 to 1/4 turn,
hold it open and then press the starter button
(see Choke when the bike has been standing for days below if hard to start).
When the bike starts you must keep the revs up or it will stall.

If you get the bike hot enough for it to idle without choke, you may find the bike stalls when you open the throttle,
simply restart with full choke, this will happen when the bike is almost ready to come off choke.

When the engine is stone cold, it will need choke for a long time.
I advise you to warm the engine up (choke on) while riding the bike,
unless you're not experienced with controlling the bike.

Riding the bike with the choke on is easy,
until you try to change down a gear since you will probably try to let the engine idle,
when of course it will just die.
The secret is to make sure you keep the engine revs much higher than idle to stop this.
Finding the choke lever while moving takes practice, try with thin or no gloves to begin with.

If the bike has been switched off for only a few hours, put choke fully on,
start the engine with a little throttle (1/8 to 1/4 of a turn), blip the throttle 3 or 4 times and turn the choke off.
I advise you to warm the engine up (choke on) without riding the bike since it's only 3 to 4 blips of the throttle.

Choke when the bike has been standing for days

See Choke above before reading the following.

The following is for the Front Disc brake model,
some of it may be true for Front Drum brake models (not all of it since their emission controls are not so strict).
The petrol evaporates over time.
If you use it every day, the bike will usually start with the first turn of the engine.
If it has been standing for a few days, it will take more turns of the engine,
every day can add an extra turn of the engine (sometimes).
At worst it could take around 10 turns.
For every 5 seconds that the electric starter is used, you must give it a 10 second rest.

I have found it best to turn the engine over once,
let it rest for 2 seconds and try again, keep repeating this sequence until you hear it fire.

If it fires once and then dies,
try the same sequence again or
try turning the engine over 2 or 3 times without a rest or
turn the engine over with the throttle closed (as soon as the engine fires, open the throttle 1/8 to 1/4 turn to keep it going).

If the bike really refuses to start and keep going,
switch the ignition key off for 30 seconds or longer to let the battery recover to full voltage, then try again.

If you have flooded the engine with petrol,
switch the choke off and open the throttle fully and turn the engine over several times.
If it still fails to start, switch the petrol tap off and turn the engine over several times,
then switch the petrol tap back on and try the normal starting procedure
(it will take several turns of the engine to get petrol back in).

When the bikes running, the petrol in the carburettor is still partly stale (gone off / evaporated),
expect the bike to need choke for longer than normal and to feel rough,
until the carburettor has been fully refilled with petrol from the tank (could take 0.5 miles).

All this trouble might be eliminated if you leave the petrol tap on all the time,
but mechanics warn that over time the petrol will seep out and fall all over the bike and floor.

Choke Design

Starting a Honda CG125 and not being able to idle with the choke on
is totally different to most other makes and models of motorcycle.
It's because the choke is very primitive.
Nearly all chokes (except the Honda CG125 one) increase the idle speed when they are switched on.
Because the Honda CG125 does not increase the idle speed, you have to do it manually by opening the throttle slightly.
All engines need both choke and the idle speed increased in order to work (when engine is too cold to work without choke).
So the Honda CG125 needs the throttle held open slightly and only then can you start the bike (while it's open).
Other makes and models of motorcycle would only start if the throttle is closed (if it was open you would flood the engine).

Sometimes the Honda CG125 might require the throttle closed
to start the engine (but the second it starts you must open the throttle).
This will only happen after at least one un successful start with the throttle slightly open,
this is because there would be some un burnt fuel in the engine.

A few people have increased the Honda CG125 idle speed to make it idle with the choke on.
This requires the idle speed to be excessively higher than the bike was designed for.
It makes it very easy to start the bike,
but it will damage the engine when it is up to heat and does not need choke anymore.
The problems of excessively high idle speeds are.
Increased Fuel Consumption.
Engine will overheat when idling for a long time while stationary and in slow moving traffic
(overheating is very bad for the engine).
Changing gear can become more difficult and even stop you changing gear
(especially when everything overheats when stationary and in slow moving traffic).
There are probably other problems of excessively high idle speeds;
I very strongly recommend you do not increase the idle speed above the designed speed.

If Idle Mixture Screw and Idle Speed Screw are not set right (see Idle Screws page)
it makes starting the bike harder and needs choke more often and for longer.
You can also reduce the amount of time the choke is needed for by improving the quality of the petrol
(see Petrol section below).


It is easy to blame yourself for a poor quality clutch,
thinking it's you not being sensitive enough on the clutch or you not getting the throttle to clutch right.

If you wear out a clutch on any make or model of bike,
I highly recommend fitting EBC clutch plates and clutch springs,
instead of the bike manufacturer's genuine parts (which might not even be the same as originally fitted).

EBC have a reputation for making high quality and performance parts including their clutches.
My clutch tests also back this up and as a result,
I would expect EBC to outperform your original clutch or at worst equal it.

Of course I cannot test every make and model of motorcycle, but I do know the quality of EBC.
They even make their clutch springs 10 to 15% stiffer,
which only makes the clutch lever very slightly heavier (the muscles in your hand very quickly adapt),
but also results in much better clutch performance and less slipping (even on a 125cc bike).

EBC make 3 types of Clutch plates for road motorcycles.
Standard CK series (that's what I have tried and are available for a very large amount of motorcycles).
and 2 Race / Sports Clutch plates (only available for some bikes).

I was able to compare the EBC clutch to my Front Disc brake models original clutch (even when both were brand new),
the EBC Clutch is so much smoother and makes off the line starts perfect every time (no juddering),
even when you make a mistake.
I did not realise it at the time, but the original plates were always slipping slightly
(nothing to do with the oil myth, even happened on semi synthetic).
The EBC plates do not appear to be slipping,
resulting in a better connection between gearbox and rear wheel (more power and smoother power delivery).


The gearbox was improved with the Front Disc brake model, so the following may not be true for Front Drum models.

The faults below are due to the clutch or gearbox overheating due to bad design.
You can improve the overheating by using better quality oil.
Silkolene Comp 4 (real semi synthetic) engine oil was not able to stop the faults.
Silkolene Pro 4 Plus 5W-40 engine oil has substantially reduced the problem (see Silkolene Pro 4 Plus for more information).
I then tried an EBC Clutch (see Clutch above), which improved things even more.

When you are in 5th gear and want to change down to 3rd or below,
you must let the clutch out in 4th gear.
If you do not, the gearbox will refuse to change down to 3rd or below,
until you let the clutch out (in 4th gear) and then pull it in again.
If you are stuck with this problem at a standstill,
with the throttle closed, let the clutch out just enough so the engine starts to connect to the back wheel,
then pull the clutch back in before the engine stalls.
When the fault is fixed you will hear a mechanical click from the gearbox.
Sometimes rocking the bike forwards and backwards while blipping the throttle also works.

The gearbox / clutch will overheat if for instance,
you race from one set of stopped traffic lights to another a short distance away on a hot day.
You will not have any problems if you let the clutch out in every gear when changing down,
but the gearbox will refuse to change down if you do not.
When it refuses to change down and you're stuck at a standstill,
with the throttle closed, let the clutch out just enough so the engine starts to connect to the back wheel,
then pull the clutch back in before the engine stalls.
When the fault is fixed you will hear a mechanical click from the gearbox.
You can also just wait for things to cool down.

Petrol Tank

The Front Disc brake model has a petrol meter and a redesigned petrol tank,
unlike the Front Drum brake model.
The following is for the Front Disc brake model.

The petrol tank holds 13.5 litres = 3 gallons.

The petrol meter reads flat out full until the first gallon (4.54 litres) has been used.

When the petrol meter needle is half way between full and empty the tank is half full.

If the petrol tap is set to on (not reserve),
the bike will run out of petrol shortly after the needle has gone past empty and gone off the scale.

The bike will normally run out of petrol when the bike is slowing down, not speeding up.
It then takes around 10 turns of the starter motor to get the engine running,
by using the reserve position on the fuel tap.
I have always opened the throttle 1/8 to 1/4 turn when pressing the starter button,
but it could be worth trying with the throttle closed after a few turns.
You may need to rest the starter motor for 2 seconds between some of the turns,
or even switch the ignition key off for 30 seconds to let the battery recover.
I advise against running out of petrol since this takes a long time and holds up traffic.

Without reserve the bike seems to run out of petrol when there is still 3.5 (normally) to 2.5 litres still in the bike,
unless it runs out while not slowing down. I have run on reserve until there was only 1 litre of petrol in the bike.
I would not go below 1 litre since the petrol may not find its way down the petrol pipe.
Reserve officially holds 2.3 litres.


This section was last updated in March 2014
(petrol is constantly changing and ethanol increasing so it may be out of date after a while).

Also see Ethanol in Petrol Warning

In the UK I very highly recommend you never use supermarket petrol in any engine including motorcycles and cars.
The only branded petrol that I would dare to put in any of my petrol engines are Shell, BP, Esso, Texaco, Jet, Gulf.
I am not alone in making the above statements,
many car and motorcycle mechanics and shops have been going on for years about never use supermarket petrol.
Supermarket fuel has been causing so much trouble over the last few years;
some shops have been telling their customers when they pick up their new car / motorcycle,
that if they put supermarket petrol in it their warrantee will be invalid.

Supermarket fuel may often be cheaper,
but you may well find your fuel economy reduces making it more expensive than branded petrol.
Your throttle may also become sluggish.
But the most worrying problems may include the purity of the petrol (contamination),
stale petrol (gone off) and not enough cleaners.
If the cleaners are not strong enough,
burning deposits will build up reducing the performance of the engine and may well increase engine wear.

If it was an emergency and I had no choice but to use supermarket fuel.
I would only use Tesco and only if they sell 2 types of petrol, the most expensive one is the only thing I would dare to use.

All but the smallest petrol stations that sell Shell, BP, Esso, Texaco, Jet or Gulf have two types of petrol.
The cheapest petrol is the standard unleaded.
The expensive petrol is their quality unleaded,
it is not only higher octane but often has more / better cleaners
and performance enhancing things in it (maybe even better fuel economy).

The expensive petrol should really be called super unleaded, but every company has come up with their own name for it.
Super unleaded often has less or no Ethanol in it compared to standard unleaded.
Super unleaded of different brands will perform differently and will depend on your engine,
so the only way to find what's best is to try them all in your engine.

Please note petrol does go off with age,
super unleaded does not sell in large quantities so a remote / small petrol station may have old stock.
Many BMW, Mercedes, Subaru cars can only run on super unleaded,
they are often found at branded petrol stations on busy roads.
So the places they go to will often have fresher stock.

From time to time any petrol station of any brand or supermarket can have a faulty batch of petrol or a contaminated tank.
If your engine suddenly shows symptoms of bad fuel, try to avoid that petrol station for a while.

Below are the results I had experimenting with petrol in my engine a few years ago.
Please note petrol has and still is changing a lot due to the UK government forcing more ethanol in to petrol.
The amount of ethanol in petrol often depends on the brand and where the petrol station is in the UK.

Super unleaded is much better than normal unleaded in at least the Front Disc Brake Honda CG125 engine.
The effects of super unleaded and the different makes will depend on the engine design,
the following results are from the Front Disc brake model Honda CG125,
another make or model of bike / car engine (or even the Front Drum Brake model Honda CG125),
might have less improvement or no noticeable improvement or improve even more.

I started off with Sainsbury's super unleaded which is only 2p a litre more than unleaded,
the bike increased in power, torque (pulling power) and the engine ran smoother.
The improvement was largest in the lower and mid rev range of the engine.

I then tried Shell Super (it's called V Power, the old version was called Optimax)
that costs 7p a litre more than normal unleaded.
The Shell Super improved my petrol consumption by more than 7p a litre,
the bike increased in power, torque (pulling power) and the engine ran smoother.
The improvement was largest in the lower and mid rev range of the engine.
That was all compared to the Sainsbury's super unleaded.
I would say the jump from normal unleaded to Sainsbury's super was small compared to the jump to Shell super.
The Shell super also kept improving all of the above the more I used it,
it took a tank or two before it slowed the improving down to a crawl.
It does claim to have extra cleaning powers to clean out your engine and improve all of the above.
It also significantly reduced the amount of time the choke is on for.

You can mix any super unleaded brand with another brand of super unleaded or normal unleaded,
but expect the improvement to only be 50% if you only have 50% super with 50% normal unleaded.

Which brand of super unleaded petrol is best for your engine I cannot say.
The best way is for you to test them yourself. You may or may not find a large difference between them.
Watch out for fuel consumption, cleaning and performance differences.
I went back to Sainsbury's super (put nearly a whole tank of it in),
immediately the bike lost most of the Shell V Power differences.
But as I used more and more of the Sainsbury's super in the tank,
the bike got slower and slower (no Shell V Power to keep it clean).
When I was down to half a tank, I filled up with Shell V Power and got half the benefits back.
This proves the engine was being cleaned by Shell V Power and Sainsbury's Super was making the engine dirtier,
like normal unleaded.
Also see Ethanol in Petrol Warning