It’s time to make your bike cool Fresh fluid and a bit of radiator care will keep your bike’s temperature in its sweet spot
Remove any bodywork obscuring the key parts of the cooling system. You’ll need clear access to the filler cap – usually under fairing panels or infills, sometimes under the fuel tank. You’ll also need access to the drain plug – if there isn’t one, you’ll need to be able to pull a coolant hose off from the lowest point in the system. Some cooling systems have bleed screws – you’ll need access to these too.
2Out with the old
Remove your drain plug, or unscrew the hose clip on your lowest coolant pipe. Do this before removing the radiator cap and it won’t suddenly gush out everywhere. Make sure your drain container is larger than the system capacity and is reasonably wide so you can catch it all. Carefully lean the bike from side to side to tease it out from every last nook and cranny, but take care not to get it on your bike’s brakes or tyres.
3Empty your header
Your cooling system has a header tank that won’t drain with the rest of the coolant. Remove the tube that feeds it to drain it out, and flush with water. Often, these will be clogged with limescale and other nasties from years of sitting with fluid in. A baby’s bottle brush will clear light deposits, or you can remove the bottle from the bike and put it through the dishwasher for a deeper clean.
Refit the drain plug (or hose), and clean the area fully. If youõve taken fairings off, combine it with a proper scrub. Itõs a good opportunity to clean the radiator fins too. Remove the radiator and use your favourite bike cleaner to soak the dirt, a soft brush to carefully scrub, and rinse the core through from behind only Ð that way you wonõt force dirt in harder.
6Fill ’er up
Coolant comes either ready-mixed, or as concentrate. Concentrate should be mixed to the ratio specified by the bike manufacturer. Only use distilled water for mixing Ð it costs so little itõs not worth messing with the old method of boiling water to remove nasties. Top the system up slowly through a funnel, squeezing hoses as you go to bring air bubbles to the top.
8Run it up
You may still have air pockets in the system and the easiest way to purge them is by running the bike at low rpm for 30 seconds. Start the bike. If the radiator cap is on the righthand side of the bike, do it on the sidestand with the cap off, and if it burps air up or the level drops, top it up carefully. Switch off the bike, screw on the cap and refit any kind of locking screw or retainer.
Radiators work best when air can flow freely, but the fins are delicate aluminium and easily flattened, reducing the efficiency of the cooling system over time. But you can perform a little light restoration. A set of tweezers can help straighten beaten-up fins. Donõt use a screwdriver Ð itõs easy to poke it in too far, and its taper will bend the fins out the opposite way.
For cooling systems with bleed points you will need to first fill the system as much as you can. Then undo the lowest bleed screw slowly Ð it should start hissing as coolant drains down with gravity, forcing the air out. When coolant starts to dribble through the bolt, lock it off and wipe up the spillage. Top up the fluid and squeeze hoses in between to ensure a thorough filling.
Fill the header tank using the same coolant you used for the bike Ð but only go to the lower mark on the tank, exactly. This way, youõll see if the level rises or lowers in time Ð either indicates a problem in the system. Bubbling, frothing or an oily paste/film indicates a serious fault. Check for small leaks or weeps that have developed in testing. Refit bodywork and trim.
Aprilia Tuono Colours Red, grey and black. Dealer £3000 Private good £2200 Private average £1800 This one 2003 model, 22,713 miles. Dealer sale, £2999 Aprilia Tuono Colours Silver and red, red and black and Fluoro red Dealer £3300 Private good £2500 Private average £2100 This one 2004 model, 16,295 miles. Private sale, £2999 Aprilia Tuono Colours Silver and red, matt black and black and red. Dealer £3800 Private good £3200 Private average £2800 This one 2006 model, 18,024 miles.dealer sale, £3899