Most modifications to a motorcycle can be measured in clinical, objective terms. Engine improvements make increased power, demonstrable on the dyno. A stopwatch can time the effect of suspension changes. New rearsets improve ground clearance by defined amount and braking components can be judged by measuring simple stopping distances. But there's one modification that can only be gauged subjectively – a new paint job. It takes some feat of engineering to make a change stand out from standard, but even the simplest of paintjobs can be enough to get you to stop and stare.

The process of spraying a motorcycle is one of those jobs that seems simple – grab a can of paint from the local DIY shop and do you best art impression by spraying it onto your fairings – but it's only after watching the experts do it properly that you start to understand all the work involved in that seemingly simple operation. We had the opportunity to see a motorcycle paint job being done.

Motorcycles come to the painter in one of two states; bog stock or in crashed pieces. A bike crash is often what prompts an motorcycle owner to do a paint job. Often one look at the cost of new parts needed to rebuild the motorcycle is enough to prompt a stylish but economically sensible approach. If plenty of panels have gone down to road, getting a motorcycle to its previous state costs pretty much what it could to do a whole new transformation.

In every motorcycle brochure and every engine specifications we see specified the 'Compression Ratio', but what is that number. The compression ratio is the ratio between the volume of the cylinder and volume of the combustion chamber. And on most road motorcycles there is a power increase to be had by increasing this ratio. There is always an optimum compression above which the increase in heat negates the proposed increase in power, and as most of you are not dealing with race engines it is wise to be conservative with increases in compression.

Typically, small increases in compression will be beneficial throughout the rev-range and larger increases in compression will benefit performance at lower revs but be detrimental to power at higher revs. For example a motocross engine would run a higher compression than a road race engine if they were both running on the same fuel.

On most older two-stroke secondhand motorcycles available in Thailand I would not recommend more than a 7:1 compression ratio and you would need to use the best unleaded fuel with a high octane rating.

To calculate the compression ratio you need to measure both the volume of the combustion chamber and the cylinder. I must have been very selective about the maths I remembered at school – how to measure volumes of cylinders was obviously deemed important enough not to forget!

Doing basic maintenance and repair on you own motorcycle can be fun and enjoyable, and it can also save you a bit of money. Replacing fork seals yourself, a common task for motorcycle available on the Thai secondhand market, can save you in some cases around 1,500 to 4,000 THB, and with a good service manual and a little patience, it's easy to do.

On a clients older Yamaha 650cc motorcycle, the fork seals were something that had been nagging for a long time. The motorcycle was still ridable, as the forks weren't shooting oil out – yet – but it was obvious that they were seeping oil, and it wasn't a condition that was going to get any better on its own.

As we always like to remind you, before you start any project, make sure you have a good manual specific to your motorcycle. For many motorcycle models you can easily get a service manual online. For our job, our service manual included a few key bits of knowledge that came in very handy, including the amount of oil the forks require, we also found some information on the Internet on how to make a tool to aid in the removal of the damper rod in each fork.

Our new fork seals, we ordered from BikeBandit. The fork oil we bought locally Although Yamaha originally specified single-weight engine oil for our motorcycle's forks, we recommend using an oil specifically designed for use as a fork oil as it will contain desirable anti-foaming and anti-friction additives. Thicker oil can be used to increase the damping of the forks, or thinner oil can be used to soften the damping if it is too strong.

You can bolt on as many go-faster aftermarket goodies as you like to your motorcycle, but the most effective way of making your motorcycle go faster is simply sorting your set-up. When your motorcycle leaves the factory gates the manufacturer has no idea who will be riding the motorcycle. So a motorcycle's suspension has to be set to a average level that can accommodate any weight of rider.

But fear not, the array of anodized adjusters that festoon your fork and shock are there to help you tailor your motorcycle to your individual weight and riding style. That's the good news. The bad news is that as well as improving your motorcycle, fiddling with these adjusters can also bugger up the handling.

But with some assistance, you should be armed with the basics to give you the confidence to approach your suspension and start fiddling as we describe what each adjuster does and what its effect feels like on a motorcycle. When riding your motorcycle, see if it has any of the symptoms we diagnose, this may point you in the right direction when it comes to adjustment. Read what suspension experts say as they explain what's happening inside your suspension – and why – to give you a greater understanding of how your motorcycle's bouncy bits work.

Modern motorcycles don't have many Phillips-head fasteners on them – at least not as many as back in the day. When used properly, the Phillips head lets the driver slip out before too much torque can be applied. This makes Phillips fasteners an especially good choice for low-torque applications like the engine covers on older Japanese motorcycles, for example. Though the specified torque may be light, decades of repeated heating and cooling cycles plus corrosion created by steel mating to aluminum can make removing aged Phillips screws a real pain.

Oddly enough, the cheesy Phillips shank found in most older Japanese motorcycle tool kits works especially well on these old case screws. Small carburetor screws and the tiny ones holding brake reservoir lids in place seem especially prone to stripping. To prevent stripping, invest in a selection of good quality Phillips screwdrivers – this is not where you want to economize. Get a quality tool in the common #1, #2, and #3 sizes used on motorcycles.

If you rewire your motorcycle, it doesn't take long before you come to the part of the connectors, and the connectors is also a part that needs to be done properly. Solder or crimp? Soldering is a bit of a magic art that needs learning and practicing. You also need a bit more time of course, electricity! Heat damage to the wire is also to be avoided.

Crimping is easier and quicker to do and learn, but can still be done incorrectly. Reliability is about the same, either process done incorrectly will fail, and even though crimps will eventually corrode, the wiring and the connector will corrode just as quickly.

Decent correct tools are also a good starting point. Would you use the cheapest spanner? So why use the cheapest crimp tool? Some advocate crimping the connectors and then to run a little solder into the joint. Personally, I don't think much is gained in most cases, though occasionally there are some connectors for which a little solder in the joint will be useful.

The lifeblood of a motorcycle, oil's the crucial fluid that keeps a motorcycle's engine ticking along nicely. It's worth knowing a thing or two about the most crucial part of your everyday ride.

Made up from a collective army of millions and millions of molecules, oil spends its days fighting friction, off-loading carbon and reducing heat within the fiery internals of a combustion engine. And to help us get a better understanding of what oil is and exactly what it does, we've asked and expert who has been working with oil for over 41 years and sells tens of thousands of liters of oil every year. If there's anything to know about oil, this guy knows it.

Oil is a lubricating product designed to prevent surfaces from rubbing together. Oil acts as a barrier between components keeping friction to a minimum. Without it, surfaces would overheat, wear and be susceptible to failure.

How often should people change motorcycle engine oil?

As frequently as possible. It's that simple. Yest, it is costly, but if you plan on keeping your motorcycle for a long period of time, it will save your money in the long term. And your motorcycle will perform better.

Headlights can be a bit of an afterthought when you're looking for a new motorcycle. We pore over engine specs, chassis performance and electronic rider aids – but the simple job of lighting the way at night often gets missed Until, that is, you get caught out in the dark, darkness starts in December already around 17:00, and you find yourself relying on the pitiful, ghostly yellow glow that barely reaches the ground, much less shows you where that next bend goes.

If your motorcycle has a truly rotten headlight – mostly older motorcycles are serious offenders – the problem may be deeper than the bulbs. On some designs, it's the reflector and lens design which don't give enough illumination, and fitting a 'better' bulb won't help very much.

But for most motorcycles, you can swap the stock bulb for a high-performance variant, that'll give more light, as well as letting you choose a different 'color' of light. Of course, the boy racer in you will be crying out for that trendy xexon-blue, with no real reason, anyway there's no real harm in that. Lots of firms will sell you bulbs with a blue tint, as well as offering bulbs with an even more 'white' light. The choice, as they say, is yours – here's how to fit 'em.

Before the ethanol problem, the main concern was that of the misguided withdrawal of leaded fuel from our forecourts. When the environmentalists jumped on the 'lead is bad' bandwagon, worldwide the countries politicians jumped on it too and we were stuck with comparatively poor quality petrol which neither cushioned our valves nor burned particularly well.

The doom-mongers prophesied wrecked head within weeks unless we used expensive LRP or a fuel additive which replaced the missing lead with an alternative valve seat cushion.

Steel bolt, alloy thread: sooner or later that will be a mix that ruins your day, especially if you're heavy handed. Care must be taken when tightening bolts and screws into alloy threads, as over tightening can pull the thread right out of the component. If it is something that is tightened regularly, such as an oil drain bolt, the likelihood of a failure increases. The good news is that the thread can usually be repaired back to its original size for a lot less than a new crank case or engine cover.

Although fatigue does play a part in a thread failure, an overzealous wannabe mechanic is usually the reason behind something like this. Not so long ago somebody cam to us with his motorcycle the alloy thread was pulled right out of the clutch cover when the inspection bolt was over tightened. It can be repaired, but cutting the next size thread is not a good option. You would go from 6mm to 8mm in this case, which is a 33 percent increase! A thread repair maintaining the original 6mm diameter is a much better option.

For this case we have chosen a Recoil stainless insert to repair the thread. You can also use Helicoils, Timeserts, Locinserts or any other to repair threads in different applications. The correct size drill is critical to a successful repair and is chosen depending on the type of material the insert is going into. We are using a 10mm drill to repair this 6mm metric thread. Obviously, the drill needs to be straight and and, since we are sealing oil, it needs to be perfectly perpendicular to the sealing surface of the alloy.