Could a bad radiator cap be at fault for coolant comign out of vent hose, occationally? It seems to only do it while the bike is running in the rpm's or going over jumps. I just rebuilt the bike any help is apprecciated!
It's not uncommon to have a little coolant leak from the system if you fill the rads completely full of coolant. As the system heats up the coolant expands and takes up more space. After a couple rides enough coolant should leak out that when the engine is at running temp the level is to max point and it stops leaking. If you fill the system does it stop leaking after a couple rides or does it continue to expel coolant week after week?
this is a good question. I don;'t know becuase every time i check it, it is low so i just fill it up. but it never used to get that low until i rebuilt my engine. then every since then it goes down, below the lip of the rad.
C'Carver - the KDX250 does not have an overflow tank.
I agree with C'Dave that it could well be normal expansion of the coolant. One way to check is after the bike cools completely, measure how much fluid is required to fill up the radiator. If it is the same after 2 or 3 rides in a row, is probably just normal expansion and you don't need to replace the coolant that is just going to spill out the vent tube anyway.