General Tips for Installing a New Motorcycle Radiator

  • 2-6 hours
  • Intermediate
  • 125-300
What You'll Need
Wrench kit
New radiator

A motorcycle radiator helps your bike run efficiently and keeps the engine cool. If you’re having problems with your motorcycle radiator, you might need to replace it.

Overflow Bottle

When you’re installing a new motorcycle radiator, you need to be sure that you completely flush the overflow bottle. If you look at it, there will almost certainly be sludge at the bottom of the bottle and this will find its way into your new motorcycle radiator.

By flushing it fully, you’ll be starting with a completely clean system so your new motorcycle radiator will last longer and run much better.


Never use regular automobile coolant in your motorcycle radiator. What you need to look for is an ethylene glycol-based coolant that has no silicates. This is important because silicates can wear down a motorcycle’s impeller blades over time and cause them to fail, often with disastrous consequences.

Add the coolant to the overflow bottle to the full mark, which will be about halfway up the overflow bottle. From there, it will fill the radiator so you’ll need to keep filling until the correct levels are achieved on both components. The coolant you put in the motorcycle radiator should be a mix of 50% coolant and 50% water. Don’t put undiluted coolant into your radiator.

When taking out the old radiator, empty the old coolant into a drain pan. Don’t let it drain into the ground as it can be toxic to animals and dangerous to the groundwater system. From the drain pan, put it into a sealed container and dispose of it responsibly. Don’t try and reuse your old coolant in your new radiator.

Air Flush

You need to be sure you flush all the air out of the system when you’re installing a new motorcycle radiator. To do this, the air has to drain from the water pump. You’ll need to start up the engine before you fill the new radiator. Allow it to run just long enough to open the thermostat to allow the air to escape.

If you don’t do this, you could end up with pockets of hot air in the system. This could cause the engine to run hot and can also cause cavitation in the engine, which can lead to permanent engine damage.

Know Your Bike

The more you know your bike, the easier it will be to replace your motorcycle radiator. Some Hondas, for instance, actually have 2 radiators while other makes and models require you to take off the fairings or even the fuel tank in order to access the radiator.

Buy a service manual before you start the job and study it meticulously. A few minutes of preparation can save you a lot of frustration later. Make sure that you have all the tools you need before you begin the job.