Smoke/Oil out breather vent on valve cover - CB350F

[Crim]

So I've noticed that when its hot out and my CB350F gets nice and hot such as sitting at a light, it will start to puff some smoke out the breather vent on the valve cover. Is this normal? What would cause this? Blow by on the rings or?

Thanks
Stephen

 

[dirtbag]

Could be many things. Blow by or valve seals. Maybe your bike is just hot. Make sure you are getting oil to your top end.

 

[bobjohnson]

Its normal as long as its not pouring out of the breather. When it gets hot, pressure in the crank case goes up. If its really humid, waters getting sucked in by the intake in small amounts, and can condense inside the engine. Also, if youre running slightly rich, fuel can get past the rings and settle into the oil. It will then boil off out the breather as the bike gets hotter. All of these things can cause "smoke" out of the breather.

Now if youre fogging an entire city block, then id start looking for problems. As long as its a few wisps, i wouldnt be concerned.

 

[Crim]

Cool thanks for the info! I was pretty sure it was nothing to worry about, but wanted to confirm.