It can be pretty traumatic, trying to buy a second hand bike, especially if you're after a powerful machine. You'll be looking at the bike through rose tinted spectacles, which could easily overlook various faults, keenness for that extra power overcoming all sane thoughts. It could end up that you're halfway to selling the bike to yourself - which will please the seller no end.
If you can contain yourself and give the bike a good look over, then you could save yourself from buying an old nail, or at least knock a few quid off the asking price.
First, make sure you view the bike in good light, many sins are hidden by darkness or neon street lamps. The general state of the bike can tell you a lot. A dirty, messy bike's hardly likely to have had much in the way of maintenance. Dirt can also hide tell tale bumps and scratches from a spill. Also check out bent levers, cracked paint around the headstock and crystallised electrolyte around the battery also suggests the bike's been dropped.
Anyone selling a decent bike should have MOTd it and the sight of a valid tax disc helps to indicate a modicum of honesty. At the same time remember that a MOT only shows the bike's met the minimum requirements at the time of the test, and doesn't, really mean anything with regards to the condition of the engine.
Check the suspension by pushing down on the handlebars, and then do the same at the back. You're looking for a smooth return action to show that the damping is in order.
Make sure there's no oil seepage and that the front fork sliders aren't pitted. Oil leaks from the suspension are a common cause of MOT failure. Forks fitted with gaiters help save the seals but can also hide damage.
Tyre condition can tell you a lot about the state of the frame and suspension, as well as the attitude of the rider. Less than 1mm of tread is illegal, but less than 2mm makes them dubious on wet roads. If there's uneven wear then either the tyre is unbalanced, the chain adjusters are out of line or the frame is bent. This may make the blke wobble at high speeds.
Spokes that are unevenly tensioned (check for an even tone by running a screwdriver over them) will also cause uneven tyre wear and can cause the wheel to break up.
Cracks in alloy or Comstar wheels will cause them to break up and there shouldn't be any dents or bumps in the rims of any type of wheel.
Run your thumb over the face of the brake discs to feel for any deep ridges - scored discs will need to be replaced, and are a sign of the owner running the pads after they have worn down to the metal. Check that the pads still have some meat above the red wear lines. This is a good way to avoid suicide.
Check the reservoir levels, especially the rear disc brake, if fitted, as this is usually neglected. Spin the wheels, being on the lookout for spongy brakes and pads that are sticking on and make it difficult to rotate the wheel. Drum brakes are simpler to check, it's just a matter of checking the pointers on the drums to see how much shoe life is left. Very work drum brakes will eventually lock up the wheel permanently.
Check wheel bearing by trying to shake the wheel along its axle - if it moves you'll have to pay out for new bearings. Check the swinging arm bearings in a similar manner these are cheap to buy but often nasty to replace. Hooked rear sprocket teeth will mean a new chain and two new sprockets, otherwise buying just one new component will result in its rapid demise.
The rear chain is often a giveaway to the rider's attitude to maintenance. Free play at the chain's centre (on the lower run) should be around one inch. Spin the wheel and feel for any tight spots - the sure sign of a worn out chain. Check the adjusters to see how much movement is left. Some people take a link out of the chain, which gives the impression of plenty of chain life.
The handlebars should swing easily from side to side. Check the bearings by jerking on the bottom of the forks.
Test all the electrics, horn, indicators, dipped and full beam, brake lights, etc. Check brake and clutch cable to see if they are frayed or cracked (on the outers) and that both levers operate smoothly. See that there's plenty of adjustment left.
Look over the engine for oil leaks, not forgetting to check the frame rails under the engine where oil leaks often collect. Many bikes have a small leak between head and cylinder which doesn't seem to matter. Oil leaks on Jap engines should be minimal.
See if the engine is cold before it's started, otherwise it may be that the owner has kept it warm to impress you with its easy starting. Rev the engine a bit and see how long it takes to get back to idle. Turn the bars to see if the throttle cable is trapped. Feel around the engine and exhaust for air leaks.
There are many different noises the engine can make that tell you something about its condition. Rattles could mean a loose camchain, slapping means the engine needs new rings or a re-bore.
Valves in trouble make a faint popping sound. Blue smoke out of the exhaust or engine breather means piston or valve trouble. Try to listen to as many similar engines as possible to get an idea of what should naturally be present - some engines should be quiet, others rattle away but are perfectly sound.
The test ride will give the final impression of the bike. Look for any wobbles, listen for strange noises and run the bike through the gearbox. You'll need a passport or driving licence as security. Unfortunately, all of this can still miss some well disguised rogue bike.
There are some unscrupulous dealers who lash up insurance write offs, advertise them in small ads, selling them from their homes as if they were ordinary punters. They use all the old tricks; switching speedos to give false mileages and thick oil in the sump to quieten down noisy engines. There's two ways to spot them. If the name of the vendor hasn't been in the logbook for very long or if they don't know which machine you're talking about when you phone up (if they are advertising more than one bike).
A final word of warning. Not everyone is out to do you. Most bikers are fond of their bikes, so avoid being over critical. If the bike's going cheap, it's because the seller admits that the bike has faults and has set the price accordingly. Haggle by all means, but don't overdo it
On the otherhand if the bike's expensive don't assume it's as good as the price indicates...
S Ginge