CBR250r engine smoking

[Seraph]

Well, just got back from the march hare earlier today and upon arrival home I noticed that the temp guade had shot up alarmingly high...and there was smoke/vapour coming out from under the gas tank on the right hand side...I removed the tank and airbox to discover the smoke/vapour was coming from a tube that connects to to the head and comes across to the right and then presses hard against the frame on the right. what could this be?? I'm rather concerned....It only does is when it's getting hot (1-2mm away from the danger zone)

[FlyingDutchMan]

What model CBR250r do you have - the MC17 or MC19? Since the tube is connected to the head theres only two things which can go through it - water or air. I'm guessing its the crank vent hose. Where does the other end of the tube go? To confirm that it is the crank vent, next time it is doing it, stop the engine and remove the dip stick. If the vapor comes out of there it's definitely something in the oil or venting into the crank case. If nothing comes out of there then it'll be water boiling.

So if its the water - it could be time to give it a flush and then refill with 2/3 water and 1/3 antifreeze/antiboil. Leave the radiator cap off and idle bike for a few mins - can you see bubbles coming out from the cooling system? You may get some initially to get rid of air bubbles in the system, but they shouldn't keep coming for ever. Rev it to 5krpm and see if any more come out. If so, then you're probably suffering from a blown head gasket.

If is coming out of the crankcase then you either water in the oil :eek: or combustion gases are escaping past the piston into the crankcase :sick:

If the gases are from the crankcase, give the bike an oil change and see if it still does it. (What does the oil that comes out look like?). BTW you should change the oil at a max interval of 5000km.

A thing to note though about the cibby - after going on a long trip the bike generally gets quite hot if you slow down to 50km/h.


Well, just got back from the march hare earlier today and upon arrival home I noticed that the temp guade had shot up alarmingly high...and there was smoke/vapour coming out from under the gas tank on the right hand side...I removed the tank and airbox to discover the smoke/vapour was coming from a tube that connects to to the head and comes across to the right and then presses hard against the frame on the right. what could this be?? I'm rather concerned....It only does is when it's getting hot (1-2mm away from the danger zone)