South West Bikers | Motorcycle Forum

Just picking folks knowledge here...

I've just replaced my radiator on the mighty trumpet 675 and have almost refilled with coolant, is there any harm or reason why you shouldn't top up with de ionised water?? Penny pinching and convenient...

By top up do you mean you already have it mostly filling with 50/50 mix?
If so then yes, no problem.

The more water the better it actually is as a coolant but then the anti-freeze protection will drop as will the anti-corrosion protection, but if it's just a small amount it really won't matter much.

Provided you haven't lost too much coolant then it will be fine.

But would want to make sure that there is still a strong enough mix if wherever you store the bike for winter incase of freeze.

Like wot they said. You really don't want to get the mixture much less than 50/50. I keep a 5l container of 50/50 mix in my workshop ready for such use.

Depends on what coolant you're using as its not a level playing field some are more effective than others. Essentially coolant lowers the freezing temperature, but it also lowers the boiling point making the water less effective at cooling the bike. We are heading to the Spanish desert on what is the hottest year on record for 4 days on track where we will thrash our bikes to death under this extreme heat. I will probably run just deionised water for this and refill with coolant upon my return.

There's also an anti corrosion element built in to any coolant so you wouldn't want to dilute it too much for that reason alone.

Thanks all,
Seems almost unanimous...

Yeah, just being tight and not spending on a litre of coolant when I only need about half a litre in a 2.4 litre system. Well within the parameters of 50/50
So, going to top up with deionised H2o...

Thank you all for your responses

Waiting for the report on your motor going bang