Coolant loss on my CR250

[Reno Ride]

Just built a 2002 CR250.  I have a set of after market radiators.  So it takes the stock radiator capacity from 38oz to around 44oz.  If I fill the radiator to the complete top I seem to loose about 4oz.  I don't smell radiator fluid out the exhaust.  No coolant in clutch oil.  And no oil in the coolant.  So I assume the radiators are just equalizing by dumping some coolant out the overflow when I am riding?

[MyckMcClung]

zip tie a little bottle to your frame at the end of the overflow hose and see. If you are using antifreeze(which you shouldn't be) it has a tendency to foam, and that foaming leads to what is called cavitation, it is air taking up space in the cooling channels, and it will cause you to spit coolant. Drain the 50/50 automotive antifreeze,Check it for signs of oil, or carbon contamination due to a bad head gasket or waterpump seal, flush it out with clean water, and fill it up with Engine Ice, or distilled water and Waterwetter.

[Coop]

Antifreeze is ok really as long as it's diluted with distilled water and not tap water. I have been doing it since the 90's. Engine Ice and Water Wetter aren't really necessary for trail riding in my opinion. Of course that is just my opinion  .

But I do agree with hooking a bottle up at the overflow to determine if that's where the coolant loss is. Did you lose that coolant the first time after the system was empty or is it every time?

[MyckMcClung]

I can understand why you run the antifreeze Coop, being a couple blocks from the North Pole, lol.
Down here you need coolant, and make sure that antifreeze is aluminum friendly.

[Coop]

I can understand why you run the antifreeze Coop, being a couple blocks from the North Pole, lol.
Down here you need coolant, and make sure that antifreeze is aluminum friendly.

Yeah that's true (both accounts). I always forget some climates are much hotter than others. And you do need to be careful what antifreeze you use. You can't just grab the cheapest stuff off  .

[Reno Ride]

Thanks for the reply guys.  My radiator fluid is a 50/50 mix that is made for aluminum.  I will install a catch bottle today and do a few laps and see what I come up with.

[ford832]

Ethylene glycol(green stuff) and water mixed at 50/50.It's both antifreeze and coolant-raises the boiling point and lowers the freezing point.I like water wetter just to be on the safe side.
If you are filling your rad to the top you are losing it out of the little tube by your cap.When it heats and expands it has to go somewhere.
I bet once you check it after it cools off from riding,it will be in the same spot after your next ride.Bike rads typically are filled about halfway from the fins to the top of the rad for this reason.With a catch tank you can fill it up and it should draw it back in but this isn't really necessary unless you ride extreme conditions.

[Reno Ride]

Ford thanks for the reply. 

[TMKIWI]

Radiators will find their own level.
As long as it does not go down any further , not a problem.

[SachsGS]

Cylinder head bolts weeping and coolant loss? Probably time to replace that head gasket (and put a dial indicator to the cylinder head to make sure it is not warped).