125cc Motorcycle Owners Club

Honda CBF125, CBR125 and Yamaha YBR125



The warranty that came with the bike from new
is probably transferable when it's sold on to a new owner even if it's 2nd, 3rd, 4th etc. hand.

In the UK the shop probably told you that if a Honda / Yamaha dealer does not service the bike,
the manufacturer's warranty is invalid,
this is a deliberate lie to increase their profits since their servicing costs are often very, very expensive for hardly any work.

If you read the UK warranty book that comes with the bike,
it should state anyone can service the bike and the warranty stays intact,
the only way to invalidate the warranty is if you do not do the servicing correctly.

For instance if you forget to change the oil at the correct mileage
and the bike then develops a fault that is due to the lack of oil change,
you cannot claim on the warranty to fix that fault.
But if you have not changed the oil and the petrol tank rusts through (very unlikely), you can make a warranty claim for a tank.

I also remember the UK government passed a law about this a few years ago,
to stop all motor vehicles begin forced to be serviced at the manufacturer's dealers, in order to keep the warranty.
Of course a dealer has no legal obligation to carry out warranty work unless you bought it from them.

Spark Plug

Often owner's manuals will tell you to clean a spark plug and check the gap every 2500 miles,
replace it every 5000 miles for example (see your owner's manual for exact mileage).

My advice is to replace it when they tell you to clean it,
since it's difficult to clean it enough or you can damage it due to cleaning.

A standard new spark plug only costs around £3 to £5 (depending on shop)
so the plugs only worth £1.50 to £2.50 when it's half used.

I use NGK spark plugs like the majority of people
and bike manufactures who believe they are the best for quality and performance.

Below is a selection of NGK plugs for your motorcycle.

The Iridium plugs may be around 3 times more expensive,
but they may well work a lot better and last up to 3 times longer.
Iridium plugs have many advantages over standard plugs, including less electrical power required.
They can ignite a leaner fuel mixture than a standard plug and give better spark / ignition of petrol.
And is less prone to petrol burning deposits (when in city traffic jams etc.).
And can work over a larger spark plug gap (due to reduced electrical power requirements).
All this may improve your engine,
like improved throttle response, more power, less vibration, better cold starting on a winter's day.
The only thing you cannot do with an iridium is put anything in it,
to measure or clean the gap since you will probably snap the iridium tip off.

I have also listed below the NGK Spark plugs for hotter engines;
they are worth trying if most of your journey is above 50 mph.
They may or may not improve your engine,
it depends on how hot your engine design gets,
but as a guide 125cc engines are often expected by the bike manufacturers to be in slow moving city traffic all the time,
not on 50 to 60 mph roads which generate far more heat (due to higher engine revs).
So they often fit a spark plug for slow city work (cooler engine so plug is designed for cooler engine).

The hotter engine spark plugs are identical to the standard plugs,
except they will get more heat out of the engine (so cool it more).
If your engine gets too hot, the performance will drop off until it cools down enough.
But if your engine is cooled too much (like when in a lot of slow moving city traffic),
the spark plug may become fowled with petrol burning deposits (so engine will splutter or stall when idling).
As soon as the engine gets back up to heat (like at high engine revs), it will burn off the deposits.

On my bike the hotter engine spark plug did not become fowled in city traffic, but I cannot guarantee this for your bike.
The type of petrol you use can have an effect,
I use Shell V Power which has extra cleaners in it, BP Ultimate and Tesco 99 also do.
The Iridium spark plugs are less prone to fowling than the normal plug.

The worst thing that could happen is the spark plug completely fowls up and the spark cannot ignite the petrol.
If this was to happen, all you have to do is put a standard spark plug (not for hotter engines) in,
I have put one of these in my bikes tool storage compartment (in the bike with my spark plug tools),
so if I needed to I could change the plug by the side of the road.

Yamaha YBR125 (spark plug gap 0.6 mm)
NGK Standard Plug CR6HSA
NGK Iridium Plug CR6HIX

NGK Standard Plug for hotter engines CR7HSA
NGK Iridium Plug for hotter engines CR7HIX

Honda CBR 125 (spark plug gap 0.7 mm)
NGK Standard Plug CR8E
NGK Iridium Plug CR8EIX

NGK Standard Plug for hotter engines CR9E
NGK Iridium Plug for hotter engines CR9EIX

Honda CBF 125 (gap 0.9 mm, it's set to 0.9 mm at the plug factory, that's what the -9 means at the end of the part number)
NGK Standard Plug CPR7EA-9

NGK Standard Plug for hotter engines CPR8EA-9

Clutch Cable

See Owner's manual and the information below.

If bike has been used, let it cool down overnight (before checking and adjusting the clearance, see owner's manual).

The cable needs to be oiled only when you notice it needs it, clutch will feel rough and needs more power.
Don't be surprised to find that's a very long time away (depends on quality of cable).

You can just replace the whole cable, cheap enough if you do not want to oil the old cable.

To oil the old cable, unscrew the adjuster nut at the clutch lever and remove cable,
put a small hole in a plastic bag and put the hole over the clutch cable,
tie the plastic bag hole end to the plastic outside of the clutch cable with tape to make an oil tight seal,
hold bag upright and pour some engine oil in to it.
If possible leave bag upright all night (tie it to something in the ceiling),
the oil will run down the cable and out the other end, put something there to absorb it.

Replace the whole cable if oiling does not make it smooth again
or some stands have broken or it stretches regularly requiring adjustment.
To replace cable,
disconnect it at the handlebar lever and at the other end which is probably on the right hand side of the engine.
Most motorcycle dealers or accessory shops should sell a universal motorcycle clutch cable that will fit.


All of the following could transform your bike if it has not already been done.
Suspension without enough grease or oil in will not only make the bike uncomfortable when going over bumps,
but will also substantially affect the cornering ability round bends and lift the wheel off the road (not to mention corrosion).

Also see Rear Suspension in General page

There is a strong probability when the bike was manufactured,
that the rear swinging arm bolt was not greased properly (or at all).
It should also be re greased every few years as well,
a red coloured grease is ideal, see Red Grease in Brakes page.
It's a very quick thing to do, if you're really not confident to do it yourself,
get a mechanic to do it, watch them work, may only take 10 minutes (so do not pay a fortune for it),
they should also have the grease.
If you find no mechanic will do it cheaply, rounding up 10 minutes work to 30 minutes or an hour,
in the UK see if they will do it when you have an MOT.

Front suspension, the forks should have their oil changed every few years as well,
it's even possible the manufacturer did not put enough in the first place.
So I recommend you change it, you need to find out how much to put in
(ask a dealer for your bike version, Haynes are not always right).

When you change the fork oil, it's probably a 10w weight motorcycle fork oil you need.
It's also the perfect time to fit fork gaiters to protect the chrome in winter.
To see how to remove the forks, see Fork Gaiters in Riding In Winter page.

But make sure you slacken the cap on the very top of the fork leg first (that's where the oil comes out).
When you have the fork out, remove the cap at the top and turn it upside down,
let the spring fall out and let the oil run out for around 20mins.
Then move the chrome part in and out of the leg a few times to get anything left out.
Then put the correct amount of new fork oil in and put the spring and cap back on.
See Fork Gaiters in Riding In Winter page again to see how to put fork back in to bike.
Then you will be able to fully tighten the cap.

Ethanol in Petrol Warning

This section was last updated in March 2012.

Ethanol is very bad for all petrol engines and will cause extreme damage if you are not careful (more details below).

The percentage (amount) of ethanol being added to petrol has and is increasing every year in the UK and many other countries,
due to governments trying to reduce the amount of petrol used.

As a result many petrol engine manufacturers ether refuse to mention if they can be run on ethanol or advise you not to use it.
Even if they say it can be run on ethanol,
the good manufactures will say you must remove it from the vehicle if stored for months.

Trying to avoid buying petrol with ethanol in it is impossible (or almost) in the UK and many other countries.

The higher the percentage (%) of ethanol in the petrol the worse the problem.

The main problems with ethanol are.
It prefers to mix with water instead of petrol.

Since all petrol tanks have a breather hole / tube,
moisture from the air outside gets in to the tank and turns to water (condenses).
Petrol and water will not mix, petrol will always sit on top of water even if you mix or shake it around.
So over time more and more water will get in to the tank and sticks to the ethanol.

When too much water sticks to the ethanol, the water and ethanol will drop to the bottom of the petrol tank.
No matter how hard you try, there is no way to get the petrol to mix back in to the ethanol.

If the water and ethanol sitting at the bottom of the tank is low enough,
it hopefully will not be high enough to go down the petrol pipe.
Since ethanol increases the petrol octane, losing it means the engine may not start or will run very badly,
but no damage will occur if you realise the problem and replace the fuel.

The real problem happens when you get pure ethanol + water going down the petrol pipe.
Ethanol is a very strong cleaner; it will dissolve glue, sealants, rubber and some plastics.
The water will corrode (rust) things.
Even if it only happens once, it's often too late,
petrol pipes and everything else between the petrol tank and the engine are often ruined.
Even if you have the best vehicle designed to run on 10 or even 20% ethanol.
The repair bill is likely to be incredibly high, so should be avoided at all costs.
Even some petrol tanks are sealed with glue or made of plastic, so even they can suffer.

Parts of the fuel system between the petrol tank and engine are also full of fuel and exposed to the outside air.
So they are also at risk.

The amount of water that gets in to the petrol tank will depend on the weather.
It's also dependant on time, the more time the more water gets in.

UK and Europe have the same rules about Ethanol since Europe writes the rules.
Up to 5% ethanol they claim can be used in any petrol engine and does not have to be mentioned on the petrol pump.
Ethanol over 5% must be mentioned on the petrol pump, since many engines cannot run on ethanol above 5%.
In the UK as of 2011 no petrol is available above 5%, but France and Germany have 10% ethanol (UK may go 10% in 2013).
The European rules state the symbol for 10% ethanol in petrol is E10 on the petrol pump;
E stands for ethanol, 10 stands for the percentage (%).
The European rules also currently (as of 2011) state that where E10 is sold,
E5 or lower must also be available at the same petrol station.
They say this normally means, E10 is only available in petrol stations that sell super unleaded as well as normal unleaded.
The super unleaded is E5 or lower, the normal unleaded is E10.

The very simple message about all this ethanol business is avoid E10 in any engine.
But any percentage of ethanol is real trouble if left in the vehicle for months.
So remove all the fuel from the petrol tank and run engine until it stops to remove the rest of the fuel from the system.
If you forget to do this, whatever you do, do not try to start engine,
since it will suck pure ethanol in and immediately damage everything between tank and engine,
you must remove all fuel from petrol tank first and put fresh fuel in.

When E10 was introduced in France and Germany, they had to have a massive advertising campaign to inform the public.
They told the public to look in their owner's manuals to see if their vehicles can run on E10.
But they also told them to check with the manufacture
even if it's not mentioned in the owner's manual since they may have changed their mind.

E10 also has many other major problems,
even in engines designed for E10 and only have fresh (less than 1 week old) petrol in the tank.
That's because it is so strong at 10% that it will attack many parts of the fuel system and engine,
even in modern fuel injected quality cars.
A engine that claims to be suitable for E10, simply has parts that are resistant to Ethanol,
but they are still eventually worn out by it.

Another major problem with ethanol (especially at 10%) is it has less energy than normal petrol.
This means worse petrol consumption.
But also means the engine runs leaner unless the engine automatically adapts.
Running to lean results in engine temperature increasing (that is a very bad thing for engine life),
poor drivability (hesitation, surging, poor throttle response etc.).

In a carburetted engine (even ones that claim to be E10 compatible), there is no way for it to adapt.
Motorcycle carburetted engines in the UK sold between 2004 and 2008 had to meet Euro 2 Emission laws,
which means they are running very lean in the first place (2001 to 2003 is a bit better, but 2009 onwards is far worse),
So making them any leaner will make things even worse.
Especially in winter, since the air is denser (since it's colder) which makes engine run even leaner.
The only hope to richen (the opposite of lean) the mixture with these engines is to allow the air filter to bung / clog up
(simply do not clean or replace it), so less air gets in to the engine.
But you do not want it to become too rich else you will also have problems.
The only other option would be to change some of the parts inside the carburettor to richen things up.
But what size parts and where to get them from may be very difficult to find (as well as making sure they are E10 compatible).

If you think a Fuel Injection engine will adapt to E10 perfectly think again,
since most cannot (including ones that are E10 compatible).
First of all the computer in the Fuel Injection system needs to have been programmed (mapped) for it.
Even if it has, you are probably thinking that since all Fuel Injection systems have an oxygen sensor,
it adjusts the engine to automatically richen / lean it to get the perfect fuel mixture.
The problem is at full throttle not all Fuel Injection systems use the oxygen sensor.
So unless you have a knock sensor (adjusts to the quality / octane of the fuel by adjusting the ignition timing),
you will have problems like a carburettor engine (see the paragraph above).
Running to lean with a fuel injection system may be worse than a carburetted engine.
Since the fuel system often does not like excessive heat (especially if the fuel pump is above the engine).
Also motorcycle fuel injection engines sold after 2009 have to meet Euro 3 emission laws,
which means they are running very lean in the first place.

More details about the problems with Ethanol
can be found from Classic Car and Classic Motorcycle places since they have more experience.
Also lawn mower places are starting to notice and petrol boats and light aircraft are suffering.

A simple test for ethanol in petrol is.
Get a clear container (with a top) that can withstand petrol.
Put a mark around 25% from the bottom of the container.
Pour water up to the mark.
Fill the rest of the container with petrol.
Put the top on and shake / turn upside down.
Turn container upright.
Immediately the petrol will separate from the water.
If there is any ethanol, it will have mixed with the water; since both are transparent they will both look the same.
So if it looks like the water is above the mark, you have ethanol, the higher it is above the mark, the more ethanol there is.