Radiator problem.

[mattjudd10]

Ok. So i just bought a 2005 crf250r and when i got it home i started it up...Let it warm up at idle and revved it and A LOT of white smoke was coming out the radiator overflow hose. The guy i bought it from said it had been sitting for along time so i assumed it was just trapped air bubbles considering he just put a brand new rad on one side. Now after i got all the bubbles out it seems fine when im riding, but if i let it idle for 10 min or longer it starts with the white smoke again and some antifreez comes out too. The head gasket is NOT blown. So i guess my main question is since these bikes aren't meant to sit at idle is it normal for this to happen if its sitting at idle? 

[mlatour]

You've pretty much answered your own question,

 

These are MX race bikes, they aren't designed to sit idling / ride around at super low speeds as they require a certain amount of airflow thru the radiators to cool the engine.

Keep overheating it too high / too often and you just might blow a head gasket after all.  

 

A cooling system pressure test might give you an idea if any damage was done.

Edited November 16, 2015 by mlatour

[WALKINGWOUNDED]

It will heat up fairly quickly without any air flow across the radiators.

 

You can't get air bubbles from setting, or trapped air in the system from setting, or not.

 

There is no thermostat, and the radiator cap is the highest point of the system; it will bleed itself when you fill it up.

 

It's possible it wasn't filled completely when the radiator was changed, or the previous owner let it idle too long, and it puked out coolant and became low.

[coryf89]

Idling for 10 mins or more?!?!? Jesusssssss.

[The Inquisitor]

Ya you do not want to let these bikes idle for 10 mins. When I stop on the trail, if I am not starting again in a minute or so I shut it off.

 

Make sure the cooling systems is filled as per the manual with the correct coolant.

[mattjudd10]

Idling for 10 mins or more?!?!? Jesusssssss.

[mattjudd10]

yes it's been sitting for years and it wasn't running right with the old gas thought I would just burn it up because the bike had been sitting so I thought that running it would be good, but I'll just empty all the old gas out and out some fresh gas in. Thanks everyone