How to Flush a Motorcycles Cooling System
Cooling system failure and subsequent overheating or freezing and cracking is the most common reason why motorcycles die. Flushing your cooling system and changing your coolant regularly is an easy ounce of prevention.
Your motorcycle manual will recommend an interval for changing your coolant, usually a number of miles or a period of time. Without a manual, you should change your coolant at least every other year, more often in extremely hot or cold climates, if you ride long distances, or if you store your bike for the winter. Your coolant definitely needs changing if it looks translucent or dirty, or if your motorcycle is running hot. If you want to get technical, you can also invest in a hydrometer.
Always use an ethylene glycol-based coolant that is labeled 'no silicate.' Silicates keep the inside of cooling systems clean, but they will also wear down your motorcycle's plastic impeller blades. This why you should never use automotive antifreeze. Mix the coolant with distilled water according to the guidelines in your owner's manual. If you don't have a manual, the default mix is usually 50-50.
Find the drain bolt on your motorcycle. Some bikes will require you to remove fairings or even the gas tank to reach the bolt. Some bikes will have as many as four drain bolts. Many bikes also have an air bleeder bolt on the water pump. Honda VTRs have two radiators.
Get a container large enough to hold all the antifreeze currently in the system. Take off the radiator cap. Remove all drain bolts. Remove the air bleeder bolt. Be ready to catch the antifreeze as soon as it starts coming out from under the water pump.
Once the flow stops, put the bolts back on and fill the radiator with water. Remove the bolts again and let the water drain out. Keep doing this until the water comes out clear. As you get more used to doing this, you may not need to keep replacing the bolts each time.
Disconnect the hose that connects the neck of the radiator to the overflow bottle so you can clean out your overflow bottle. It will probably have a thick layer of sludge on the bottom. You can remove your overflow bottle, or you can flush it out in the same way as your radiator. Some overflow bottles are very hard to get to.
When the water comes out clear, let the system drain out completely. Put the bolts back on.
If your motorcycle has an air bleeder bolt, you need to remove it to drain out all the air in the system. First, let the air drain out of the water pump. Then start up your engine, running it long enough to open the thermostat and let any trapped air escape. It is important to get all the air out. Pockets of hot air will make your motorcycle run hot. They can even result in cavitation that can damage your engine. Triumphs and some other motorcycles are particularly susceptible to air pockets.
Fill the overflow bottle to the 'full' position. This will be about halfway to the top or less.
Put the bolts, fairings, radiator hose, and any removed parts back together. Take your used antifreeze to your local garage or dealership for proper disposal.
While changing your coolant, never store antifreeze near where your dog or cat can get to it. Antifreeze has a sweet taste irresistible to dogs and cats, but it is also very poisonous. It doesn't take much to kill them.
