Topic: Help - water vapor in exhaust after top-end work

[neudl]

I just finished replacing rings and all top end gaskets.  Everything is together, and the bike is running well except one problem.  It is idling a bit rough, and I noticed that there is white smoke coming from no. 2 and 4, and water is condensing at the end of these pipes.  If you hold your had in the exhaust stream, it feels like some spray (or I could be imaging that part).  The engine is a '72 CB500, everything else, including carbs, is from a '77 CB550. Anyone have thoughts as to where I should start?

[gtyler5]

are you sure it's water and not gas? if one or two of the cylinders are not getting spark it could be spitting the gas out the exhaust and this would make it idle rough. could also be a carb issue, one or two running lean needs sync'ed or float adjusted..that's what I would start with. hopefully one of the pro's will chime in here, I'm just a rookie..

[neudl]

I should add that I just pulled all of the plugs, and all are as clean and dry as a whistle.  I set the timing with a strobe, It was a bit off.  Dry compression on a luke-warm enginge was 150, 147, 140 (did #3 last and the engine had cooled more), 147.

[TwoTired]

If you still have white vapor coming out after a 15-20 minute cruise on the freeway, then worry.

Collected condensation takes a while to thoroughly heat and vaporize the condensation.

You should also check the low point drain holes in each muffler.  Blocked ones mean more water buildup.

Cheers,

[neudl]

When you say worry, any thought on what to worry about?  I am guessing carbs?

[TwoTired]

     Ha, Ha, dang that's funny.

I tell you it's water vapor from condensation and you have an air cooled engine.  Where would the water come from after it's all boiled off?  Worry about someone secretly filling your mufflers with water when you're not looking?  Maybe your local Fire department is bored and since you looked at them askance...
You could worry about materializing in an alternate universe where the laws of physics are all different.

Why are you so determined to find something dire wrong with your bike?   

You could worry that it is not white smoke, but blue smoke, where you have to rebuild the entire engine to correct it!
Or, you could worry that it's actually black smoke, and your carbs are so shot, you will have to manufacture new ones yourself!

How that?

 
I wonder... Is your brow permanently furrowed from constant worry?
I'm jesting, btw.  Just ignore me.
Cheers,

[neudl]

No offense taken - I am definitely a worrier.

[bozo4onion]

Make sure the leaking water has not emptied the radiator. It is located behind the engine control module under the fuel injection pump. Good luck.

[merc2dogs]

also, some fuel blends are very prone to produce water vapor.
 certain times of year BP gas makes my bike steam, most of the time it doesn't.

ken.

[bozo4onion]

How does fuel produce water vapor? There is no water in fuel. Does ethanol absorb some?

[kslrr]

How does fuel produce water vapor? There is no water in fuel. Does ethanol absorb some?

Fuel is a "Hydrocarbon".  The Hydrogen component that burns (combines with Oxygen) produces H2O (water).  Once the engine is warmed up, the water is still there in the form of high temp steam which can not be seen and does not collect in the exhaust system.  That is why it is bad for an engine to be used often on short trips (engine not completely warmed up) rather than on long outings.

[wesniles]

In an internal combustion engine that burns gasoline, if your air to fuel ratio is "perfect" (thinking back to college, internal combustions engine theory class, i believe its called the stoichiometric fuel ratio) you should have only 2 things coming out of your exhaust after complete combustion, H2O and CO2.

[merc2dogs]

 One of many links I found on water absorption:

http://www.fuel-testers.com/expiration_of_ethanol_gas.html

 Been a problem for me lately as I have always kept gasoline around for emergencies, and I found that newer blends don't last as long.
   A while ago my old volkeswagon (sold now) steamed, and I looked into the cause, found it was ethenol blends, switched over to a non-blended type and it stopped, today every station is a blended fuel so I have to live with the steam and reduced mileage I get from some.
 
 Some stations don't seem to have as much of a problem as others.

Ken.