carbtune synchronizer and XJ 700X

I am now at the point of synching the carbs for the first time ever and I did get a carbtune. Here is my question. According to XJ700 manual, "Vacuum Pressure at Idle Speed" 24 kPa, 180 mm Hg, 7.1 in Hg" :?: Now according to Carbtune instructions, if a bike is recommended to have readings lower than 8cmHg, the Carbtune Pro must be hung upside down. Here's where I get confused: 180 mm Hg should equal 18 cm Hg, which can be measure by carbtune in it's upright position. I don't get the "7.1in Hg" it seems contradictory. I don't much want to start a synch with everything ass-backwards. Could someone who knows the XJ 700X, please tell me if my theory about the 18cmHg is correct? Thanks!

 

Don't worry about the actual numbers.

Try the CarbTune in its "upright" position, if you get solid enough readings to sync, use it that way.

If not, flip it over. The numbers themselves aren't critical; the comparison between cylinders is what matters.

 

okay, you are pretty much echoing what the carbtune manual says about comparisons being far more important than numbers. And it's easy enough to see very quickly whether I'll get usable readings in the upright position. Thanks for an injection of common sense

 

Just an FYI to help ease some confusion all three measurements are equal. They are just different scales for measuring pressure/vacuum.

24 kPa = 180 mm Hg = 7.1 in Hg

 

Bigfitz is correct.

dave f

 

I grasped that. But both the 2nd and 3rd scale are designated with "Hg" so what is the difference? Is 7.1 specific gravity or something like that? My carbtune instructions make reference to cmHg, which makes me think that using their scale means converting from 180mm to 18 cm.

 

Hg is the designator for mercury. Which is what the old vacuum gauges used as a measuring medium. It measured how far the mercury was moved.

mm Hg= mm of course is metric for millimeter. Hg for mercury. Millimeters of mercury
in Hg = SAE measurement for inches. Hg again for mercury. Inches of mercury

Two different ways of saying the same thing. 7.1 in = 180mm

While mercury is no longer used due to the toxic/poisonous nature of the substance. The term is still used.

kPa is a scientific newton based measurement and is seldom used in instruments such as the tools that would be used on bikes.

Ghost

 

thank you, Ghost.