White smoke and water coming out of exhaust.

[Tristan]

Hey guys..I really should start using my build thread again, but I know I'll get a response faster if I just post in the help section.
Bike: '74 cb350f
Outside temperature: 48 degrees


So, my top end has been rebuilt. I installed new rings,lapped the valves, installed all new gaskets and valve guides, had my mechanic hone the cylinder walls and adjusted the timing, points gap and valve tolerances.

My bikes been sitting in my unheated shed all winter and I finally got around to starting her up for the first time today. She runs fantastic with no hesitation when revving up.

After about 20 seconds, a fine white smoke started to come out of the exhaust, and a small accumulation of water also formed at the end of the muffler. Its hard to tell if what Im seeing is smoke or steam, but it completely dissipates within a foot of the muffler, and if I put my hand close, it gets very moist, leading me to believe that its water vapor.

Ive let it run up to 5 minutes at idle and the smoke doesn't seem to be toning down at all.

Any ideas?

 

[teazer]

Run it harder.. ;-) Seriously. It's water in all probability and at idle, pipes do not get hot enough to dry out.

 

[VonYinzer]

Yup, condensation from temp changes. Ride it for an hour or so. Should go away. DO NOT let it sit unused for any long period of time now until you dry it out. It will start to rust the pipes from the inside.

 

[Tristan]

That is exactly what I was hoping to hear!! Man, my heart sunk a little when I saw that smoke, nice to know its probably nothing to be concerned about. Ill have an update in a few days with the verdict.

Thanks teazer and von!

 

[AlphaDogChoppers]

Water vapor is a by-product of combustion. If the ambient conditions are cool and near the dew point, you will see clouds of vapor from any engine's exhaust. It's totally normal to see drops of water coming out of mufflers. Many exhaust systems have a small drain hole in the bottom of the mufflers to let the water drain out.