Motorcycle servicing explained | Bike Social FAQ

Eugene Chartell is KTM UK’s workshop manager

Regularly servicing your motorcycle will not only prolong its life, it’ll allow you to get the best performance from it.

Eugene Chartell started stripping the top-ends of bike engines down when he was just nine years old. He’s been a race mechanic on motorcycles and cars (covering F1 support races), and also racing bikes himself in motocross and National Junior Superstock. He did his apprenticeship with a Ducati dealer, has spent time with Yamaha, and is now the workshop manager of KTM UK in Silverstone. We asked him what goes on in a typical bike service, when it needs doing, and why it matters…

How to get the most out of your motorcycle’s engine oil

Oils are so advanced now that the typical rider won’t see any problems if it’s changed at the recommended intervals. Of course, it depends on how you ride, but unless you’re putting your  engine through very extreme stress – for instance by racing – the oil will easily go the distance.

The filter should be changed with the oil – it’s a relatively inexpensive part, and unlike some cars that allow a filter change every other oil change, a motorcycle engine works a lot harder. Some bikes, like this KTM, have one or more mesh screens fitted to further filter the oil – in this case they can be washed, but a complete kit of filter, O-ring and two mesh strainers costs about £38. The filter alone is around £11.

Many bikes have a ‘canister’ oil-filter, typically mounted at the front or bottom of the engine – the disadvantage with these is that they can be easily damaged. BikeSocial knows of one biker whose canister-type filter was punctured by a stone, which caused oil to spray over the rear tyre. KTM uses a cartridge-type filter that’s tucked away inside the engine, making it less prone to damage.

Some bikes – typically more specialist machines like the Honda CR450 – use a separate oil for the engine and transmission, whereas you’ll usually find your motorcycle takes one oil in the sump to lubricate the engine and integral gearbox. Bike oils are different to car oils as they’re designed to soak the clutch plates – a car oil will cause it to slip.

Even in older Ducatis, which had dry clutches (hence the distinctive rattle sound), a specific motorcycle oil must be used, not least because it needs to deal with the sheering forces of a gearbox.

When checking the level of your bike’s oil, consult your owner’s manual first – some machines have a very specific procedure, and checking while the bike’s cold might lead you to believe that the level’s low when it’s not; overfilling an engine can be almost as damaging as starving it of oil

On this KTM 1050 Adventure, the filter and 3.5litres of 10W50 oil should be changed every year or 9,300miles (15,000km), whichever comes first.

Why motorcycle valve clearances are so important

Checking the valve clearances on your bike is very important, and is simply a case of setting the engine to a specific crank position, then using a feeler gauge to check the gap between the cam lobe when it’s off its tallest point, and the follower, which is what pushes the valve open; measurements are usually started at TDC (Top Dead Centre), which is where the piston in number one cylinder is at its highest point of the compression stroke.

It’s an easy check, but getting to the cams in the first place is a big job, which is why it’s one of the most expensive service bills on a bike. In the case of many motorcycles, any bodywork has to be stripped before the tank comes off, then the airbox taken out, the radiator swung away and the cylinder head covers removed.

Often, valve clearances on modern quality motorcycles that have been ridden on the road are within tolerance at the first inspection – the manufacturer will give a minimum and maximum gap. By the second inspection they’re more likely to need adjusting – usually with varying thicknesses of small shims that sit under the follower in a ‘bucket’. To do this, the mechanic will note down all the clearances (these are recorded on a central database – along with every other maintenance record – on all KTMs), then remove the cams to get to the shims. Each one must be kept in order, so the technician can measure the shim’s thickness with a Vernier caliper, then work out what size shim he or she needs to replace it with to get the correct gap. New shims are measured before fitting into the relevant followers, the cams refitted and the gaps checked again.

Some bikes – a good example being the Honda C90 – use a screw-type adjuster in the tappets that follow the cam. This is a lot simpler, and certainly on a machine like this – which has very easy access to the engine – the cost impact should be minimal.

Whatever system is employed for setting the valve clearances, the measurements have to be taken with the engine absolutely stone cold. This KTM was taken to the workshop on a trailer, as otherwise the mechanic would have had to have waited a very long time to make sure the motor had no heat in it.

What happens if I ignore my valve clearances?

When valve clearances do need adjusting, they’re almost always too tight – this is because the valves start to bury themselves into the seats in the head, so the valve’s stem rises, getting closer to the cam. If they go too far, the bike will become harder to start, will backfire on the over-run, and lose power.
Over-tight valve clearances will lead to increased engine wear and damage; the cams will suffer more wear as the followers are in contact with them for longer, the valve seats will become damaged, and the potentially increased running temperature could cause problems in other parts of the engine.

Some wear is normal on the valve – the light polishing seen on a healthy set will likely have happened in the first few minutes of the bike being run, often when it was spun up on the rolling road as it came off the production line.

Some light wear on the cams is normal

How can I reduce the wear on my engine’s valves?

In order to keep the valves within their tolerances as long as possible, always use the correct grade of engine oil.
Over-revving your bike too much will also accelerate the wear due to the valve springs resonating. At very high frequencies, they can start to ‘bounce’, which causes them to open the valves without the cam’s timed assistance.

Using the wrong fuel can also have an impact – for most road riders, typical premium unleaded is fine, but some people believe that the higher the octane, the more power their engine will make. This becomes an issue when octane booster additives are put into the tank along with very high-octane fuels (often used in racing or at track days). This combination can run extremely hot, pushing an engine beyond its capabilities.

KTM specifies that the 1050 Adventure’s valve clearances should be checked every 18,600miles (30,000km).

Mechanics will use a suction system to draw fresh brake fluid through your bike

When to change your motorcycle brake fluid

While a racer will need to change their brake fluid far more regularly due to constantly getting it very hot, the average road rider need only stick to the manufacturer’s recommended intervals. Brake fluid is ‘hygroscopic’, which means it loves to absorb moisture from the air; as water boils at 100°C, the more of it is in your brake fluid, the more spongey the brakes will feel, and ultimately the more likely they are to fade when used hard. As this absorption happens over time, it’s important to change the fluid at the specified times.

Most bikes use a DOT 4 fluid – a standard set by the Department of Transportation for minimum specifications. There are two boiling points; dry and wet. Dry is the boiling point of the fluid when it’s brand new; wet is the boiling point after it’s been in the system for a while, and has absorbed 3.7% of its volume in water.

DOT 5.1 is a glycol-based fluid that is compatible with DOT 4 fluid, and simply boils at a higher temperature. Don’t confuse it with DOT 5, which has the same higher boiling point, but is silicone-based, and must NOT be mixed with glycol-based fluids.

Brake fluid can typically be changed on a new bike equipped with ABS in just the same way as an older machine, but it’s very important that air is not allowed to enter the system during the process – if it does, you’ll need to go to your dealer so they can prime the pump by hooking it up to the computer.

KTM recommends Motorex fluids, and this company’s DOT 4 data sheet claims a wet boiling point of over 165°C, and a dry one of over 260°C.

The KTM 1050 Adventure should have its front and rear brake fluid changed every two years. The hydraulic clutch on this bike uses mineral oil, which should also be replaced every two years.

Should you service motorcycle suspension?

Degradation of your suspension is a very gradual thing. Many OE shock absorbers are deemed a sealed unit, but the oil in your forks can usually be changed by any dealer. It’ll be a long time before it needs doing, but the problem is that, being such a gradual thing, you’ll probably not realise the handling has gone off.

KTM doesn’t give a specific recommendation regarding changing the fork oil as it should be assessed as part of a bigger inspection of the front suspension, and carried out according to use. A racer would change the oil regularly as it’s put under a lot of stress and can have a real impact on lap times, but for a street rider there’s far less need, so it’s really down to owner discretion.

We spoke to Chris Taylor of K-Tech Suspension for advice on servicing: “Suspension is similar to an engine in that it’s a moving component that uses oil to create forces, to lubricate and goes through heat cycles (although not at such high temperatures). 

“Keeping this in mind it’s always good practice to service forks and shocks on a regular basis, though obviously this differs from road to off-road and racing use due to the temperatures reached in operation. For road bikes I would say the norm would be around every 10,000miles, while a competition shock might be around 20hours. 

“A service would consist of stripping the units to the bare number of parts and cleaning everything, including the shims. A fork service would typically cost £338.47 – £115 in labour, the rest in parts. We also sell service kits for most makes of shock absorbers, which includes oil and dust seals, piston rod bush, piston rod lock nut and all the O-rings for £23.94. Labour would again be £115.”

While some of KTM’s bikes – like the Super Duke R – have a dealer-rebuildable shock, the one fitted to the 1050 Adventure is termed as sealed. However, K-Tech CAN rebuild this shock, potentially saving a fortune over replacements when it gets tired. Any bike’s suspension should be inspected at every service.

When to change motorcycle engine coolant

The coolant in your bike – assuming it’s not got an air or oil-cooled motor – doesn’t just stop the engine getting too hot; it also prevents corrosion in the narrow pathways inside the engine, and lowers the freezing point. If you just put water in there, not only would there be a build-up of rust and limescale, the liquid could freeze, at which point it expands and can crack the engine (it’s why you might find expansion plugs built into some motors, just in case this happens). Over time, the protective qualities of the fluid degrade, so it needs to be replaced.

If you have to top up your cooling system between services, first question where the liquid has gone. If there are oil deposits in the fluid, it could be a sign of a damaged head gasket. Another indicator of this is a mayonnaise-like substance in the engine oil, though this can often be seen in small quantities due to condensation, especially if the engine is started but not allowed to get up to temperature. If all is well, you should only use de-ionised water, not plain or boiled water. However, as coolants are now available ready-mixed, and are far more compatible with each other than they used to be, you can top up very easily.

If you have an older bike with an unknown coolant in, it should be thoroughly flushed before replacing.

The KTM 1050 Adventure’s coolant should be replaced every four years.

Some water had corroded this plug, but it doesn’t affect performance

When to change motorcycle spark plugs

Getting to the spark plugs on a bike can be a time-consuming job. With modern machines having overhead cams, the plugs tend to be buried down inside the cylinder heads, so it’s often necessary to remove the fuel tank and airbox.

Some corrosion might be visible on the outside of the plug, where water has got in (usually due to over-aggreassive washing), but some bikes – like this KTM – have drain holes to allow the majority of the water to flow away. While plugs only generally need changing after a certain mileage – rather than time – if your bike isn’t getting used a lot, it’s worth keeping an eye on them for more severe corrosion.

Valve clearance checks and spark plug replacement will likely fall on the same service, as getting to this area is so labour-intensive.

The KTM 1050 Adventure has two plugs in each of its two cylinders, which should be changed every 18,600miles (30,000km).

When to change your motorcycle’s air filter

A clogged air filter will cause your engine to run poorly, and in extreme cases, dust and grit could find its way into the motor with potentially devastating consequences.

For the average road-rider, sticking to the recommended service intervals will be fine. However, those riding in extreme locations – for instance across deserts – will need to change the filter more regularly. The tank will most likely need to be removed, but then accessing the filter is usually a simple job.

The KTM 1050 Adventure’s air filter should be replaced every 9,300miles (15,000km). If riding in very dusty areas, an upgraded filter is available, along with ‘socks’ that cover the air intakes.

KTM’s XC1 is used by dealers for diagnostics of your bike

Servicing and motorcycle diagnostics / fault codes

Modern bikes have a lot of electronic systems fitted, and European regulations now state that the fuelling data must be accessible for checking. Like cars though, each manufacturer has specific technology, and will have its own computer systems to check and edit.

KTM’s XC1 is basically a large ruggedized tablet that plugs into the bike and allows the adjustment of various parameters, and the resetting of fault codes.

There will usually be some faults stored that wouldn’t have affected the rider – sometimes simply turning the bike on and off too quickly can generate one, or running it on a paddock stand or dyno as the ABS gets confused by the mismatched wheel speeds. Wheelies can cause the same code to flag up.

While dealer-specific tools like this restrict the abilities of independent workshops, they can be used to more quickly identify faults.

A specific tool used by KTM dealers can also identify breaks in the wiring loom – very useful on the complex CANbus systems of modern motorcycles, especially if the owner has fitted their own after-market electrical accessories.

These reed valves control recirculated air in the engine

Additional service items and checks for motorcycles

Every bike might have specific parts that also require checking or replacing – on the KTM 1050, one such job is the secondary air system membranes; a pair of reed valves that control the flow of gasses from the crank case back into the air-box. These can weaken over time, but are easy to access and should be replaced every two years.

A service will include an inspection of the bike – this will cover maintenance items like brake pads and chains and sprockets, which could need replacing, but also checking for worn fork seals, the state of the tyres, that all the fasteners are tight, and even for structural damage to the chassis. A skilled mechanic will understand what kind of life a bike has been having, and what areas could have been damaged, maybe by being dropped off-road.

Besides the service items listed above, here are the checks required during a KTM 1050 Adventure service:

• Read fault codes using diagnostic tool

• Check fuel pressure

• Check electrical equipment (eg lights etc)

• Check brake discs and pads

• Check tyre condition and pressures

• Check brake fluid

• Check brake lines

• Check suspension for leaks and damage. Also clean fork dust boots.

• Check chain and sprockets for wear and tension

• Check coolant level

• Check radiator function

• Check cables for damage, and for routing with no sharp bends

• Check steering head bearings for play

• Check headlight position

• Check oil nozzle for clutch lubrication

• Check swingarm bearings

• Check wheel bearings

• Grease all moving parts

• Check all hoses for cracking, leaks and incorrect routing

• Check the antifreeze

• Check clutch fluid

• Check all screws and nuts for tightness

• Check for roadworthiness

• Check emissions with diagnostic tool

• Reset service interval display

At the end of the service, the technician will take your bike for a test ride to check that everything’s working correctly and that it’s safe to give back to you, unless you specifically ask for something like worn brakes to be left, in which case they may deem it unsuitable for them to carry out a road test.

A well-maintained bike will last longer, perform better and ultimately be a safer machine.