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Missing Mercury

  • Thread starter Thread starter TCARTER
  • Start date Start date
Don't confuse viscosity with weight. Oil is lighter than water even though it is more viscous. It is the high weight of the mercury that keeps it from flying into the engine and hovering in the tubes. I don't think oil will work at all - unless someone who has actually done it answers the bell.
 
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The fluid chambers in the mercury gauges are vented to atmosphere, only the weight of the mercury keeps it all from going up into the engine. This gives a reading that is measured in inches of mercury, which you could compare to a different motor, or to a set number in some manual or something...

The manometers using lighter fluids, water, oil or whatever are sealed. The fluid goes up the tubes only so far, because no air can enter the chamber to replace the fluid as it goes up into the tubes. They only go up a little distance regardless of how much vacuum there is. You can only compare and adjust the difference between cylinders, you don't get an absolute vacuum reading. All you really need is to compare them to each other, not to a standard, so this is fine.

To use water or any lighter weight fluid with an open chamber would take a vertical tube length of perhaps 10 - 20 feet, depending on the weight of the fluid.
 
Who cares what the vacuum is measured in as long as all four carbs are the same.
You can put restrictors in the tubes that help keep the fluid from being drawn into the intakes.
That was a problem even using mercury.
I have a manometer back from my 75 Gold Wing days....it no longer has mercury in it. Do I have to splain where it went?

All one needs to know is are the four carbs balanced-it doesn't matter what it reads on the scale.
If vacuum is a problem then there are other problems to be solved before synching the carbs.

If you don't want to concern yourself with the fluid get a vacuum gauge manifold. Actually easier to use.
 
I have a manometer back from my 75 Gold Wing days....it no longer has mercury in it. Do I have to splain where it went?

May I guess that it evaporated? From my understanding of Hg, since it is a liquid it will evaporate if not kept in a sealed container. I can't imagine the rate of evaporation is quick but I have had limited exposure to working with Hg.
 
No, it got sucked into the intakes.
Twist the grip too quickly and away it goes. haven't used that type of manometer since...

A manometer can be made using any kind of fluid you like as long as the vacuum doesn't pull the fluid into the engine.

My old manometer is hanging on the wall here-I'm thinking about putting 250wt gear oil in it.
I may even try used motor oil. What have I got to lose?
 
I don't think anybody is arguing that you only need to balance carbs relative to each other.

The issue has been explained pretty well that the mercury tubes are open to the atmosphere and the only thing keeping the mercury from being sucked into the bike is the weight of the stuff. Oil won't work because it is light and viscous (the opposite of mercury) - the air from below will blow through it while it sticks to the sides of the tube, telling you nothing. In fact, the thicker the oil, the worse it will work.

I'm in the process of sealing the bottoms of the 4 tubes and putting some colored water in them. The sealed tube should prevent the water form being sucked into the carbs. We'll see.

I'll let the original poster know if it works.
 
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