Carb balancing question and does anybody stock K&N filters?

**Madness** · 11th March 2012, 17:47

http://faq.ninja250.org/wiki/How_do_...carburetors%3F

**Laava** · 12th March 2012, 06:21

Originally Posted by pete376403

It looks like the four tubes are joined at the bottom. Can't see how it would work assuming the top of each tube is connected to a vacuum port in the inlet manifolds (ie one tube per manifold port). Manometers that I have used have been a U tube, open at one end and the vacuum is applied to the other end, and the fluid rises up the vacuum side of the U proportional to the degree of vacuum.

The manometer is designed to test the individuals vacuum compared to another. If one end is open to aptmosphere, it will simply suck thru into engine.
nzspokes, simple is best. You should us one tube with a large loop of approx 1m height and any oil is OK. I use atf in mine. It is fail safe. If you have probs then you have other issues. Motor must be warm and you leave the tube attached to the vacuum on the one carburettor that is non adjustable. ie, one of them [no 3?] will be fixed in order for the others to be adjusted to it. Make the idle high and be patient.

**pete376403** · 12th March 2012, 14:29

Obviously physics has changed a lot since I went to school but refer to "liquid column guage" on this page http://en.wikipedia.org/wiki/Pressure_measurement.

Quote -"Liquid column gauges consist of a vertical column of liquid in a tube that has ends which are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. A very simple version is a U-shaped tube half-full of liquid, one side of which is connected to the region of interest while the reference pressure (which might be the atmospheric pressure or a vacuum) is applied to the other. The difference in liquid level represents the applied pressure"

Four cylinder - four tubes, all fastened to a board so direct comparisons between the tubes are possible.

**Laava** · 12th March 2012, 19:44

You are right Pete but in this case the pressure difference we are talking about is so great that the oil gets sucked through the hose as it does not have enough head to retain in the tube. So it is far easier to compare two pressures, ie, carbs, which should be the same and in fact can be adjusted to be equal.