carbtune vs beer bottles

[John Croucher]

If I understand it right. It appears that both types are measuring the vacuum at the manifold and that it's just two different tools to do the same job.

I think I got it?
Tom

Kinda right.

You are measuring and calibrating to inches of mercury.  Not inches of some other liquid.  Mercury is over 7 times heavier than water.  The scale marking of a water filled gage would have to be over 7 times greater between marking to equal 1 inch spacing between mercury markings.  Also, the i.d. of the column (tubing) determines the spacing on the scale. 

There is a specification on what the mercury column weight/height should be on an idling engine.  There is a tolerance between two or more intake points also. 

If you use a light liquid verse mercury, You could be really close if the two columns (or more on multiple cylinder)  with a light liquid and a difference of 5 inches between any of them. 

Unless you calculate column/tube i.d., liquid weight, scale spacing ratio, the accuracy of a home made set up is a guess.  Go buy some real gages.  The new vacuum gages work great. 

Save the liquid in a tube for a level between two points.

[Kiwi_Roy]

Kinda right.

You are measuring and calibrating to inches of mercury.  Not inches of some other liquid.  Mercury is over 7 times heavier than water.  The scale marking of a water filled gage would have to be over 7 times greater between marking to equal 1 inch spacing between mercury markings.  Also, the i.d. of the column (tubing) determines the spacing on the scale. 

There is a specification on what the mercury column weight/height should be on an idling engine.  There is a tolerance between two or more intake points also. 

If you use a light liquid verse mercury, You could be really close if the two columns (or more on multiple cylinder)  with a light liquid and a difference of 5 inches between any of them. 

Unless you calculate column/tube i.d., liquid weight, scale spacing ratio, the accuracy of a home made set up is a guess.  Go buy some real gages.  The new vacuum gages work great. 

Save the liquid in a tube for a level between two points.

Sorry, as someone who spent much of my working life figuring out how to measure stuff in an industrial setup I must take exception.
In the case of a throttle balance manometer we are not really interested in measuring relative to atmospheric pressure just the pressure difference between left and right manifolds and we don't really care about the numbers so we don't need a scale marking. Water is fine for that although I prefer something lighter still, engine oil as it has the added advantage of a high viscosity with it's added damping
Mercury is 13.663 times as dense as water. yes you can if you want to measure inches of mercury using water or oil or any other liquid for that matter.
The ID of the column has nothing to do with it, for a given pressure the fluid rises the same distance up a small tube as a large tube, its pressure and density that matter.
A manometer is a real gauge, it's used as a standard to set Bourdon tube gauges against.
The problem with using Bourdon tube gauges is you now have 2 or more "Gauge pressure" numbers you have to juggle in your head
With a "U" tube manometer you just have a single "Differential Pressure" which you only need to reduce, you are not really interested in the exact magnitude of.


(Changes in red)

[gearman]

Sorry, as someone who spent much of my working life figuring out how to measure stuff in an industrial setup I must take exception.
In the case of a throttle balance manometer we are not really interested in measuring relative to atmospheric pressure just the pressure difference between left and right manifolds and we don't really care about the numbers so we don't need a scale marking. Water is fine for that although I prefer something lighter still, engine oil as it has the added advantage of a high viscosity with it's added damping
Mercury is 13.663 times as dense as water. yes you can if you want to measure inches of mercury using water or oil or any other liquid for that matter.
The ID of the column has nothing to do with it, for a given pressure the fluid rises the same distance up a small tube as a large tube, its pressure and density that matter.
A manometer is a real gauge, it's used as a standard to set Bourdon tube gauges against.
The problem with using Bourdon tube gauges is you now have 2 or more "Gauge pressure" numbers you have to juggle in your head
With a manometer you just have a single "Differential Pressure" which you only need to reduce

Amen brother

[John Croucher]

Sorry, as someone who spent much of my working life figuring out how to measure stuff in an industrial setup I must take exception.
In the case of a throttle balance manometer we are not really interested in measuring relative to atmospheric pressure just the pressure difference between left and right manifolds and we don't really care about the numbers so we don't need a scale marking. Water is fine for that although I prefer something lighter still, engine oil as it has the added advantage of a high viscosity with it's added damping
Mercury is 13.663 times as dense as water. yes you can if you want to measure inches of mercury using water or oil or any other liquid for that matter.
The ID of the column has nothing to do with it, for a given pressure the fluid rises the same distance up a small tube as a large tube, its pressure and density that matter.
A manometer is a real gauge, it's used as a standard to set Bourdon tube gauges against.
The problem with using Bourdon tube gauges is you now have 2 or more "Gauge pressure" numbers you have to juggle in your head
With a manometer you just have a single "Differential Pressure" which you only need to reduce

Technical manual for multi cylinder, multi carb/injection manifolds have a calibration vacuum number.  Not just a balance point.  This balance vacuum is usually measured in inches of mercury not water or transmission fluid. 

Both pressure and density are factors in how far a liquid will differentiate between intakes.  Mercury density is 13.6 times that of water.  Your scale for a less dense liquid has to be adjusted accordingly if you are balancing to industry specifications.  If you are using a lighter liquid like water in the hose, the levels could be different by 7.8 inches and be the same as 1/2 inches of mercury.   

[Kiwi_Roy]

If you wanted to measure the manifold pressure with a mercury manometer you would need one at least 30 inches high, not that your manifold will pull down that far but if you suddenly apply a Vacumme or pressure to a mercury manometer its very easy to lose the mercury out the top, once it gets moving the momentum would easily carry it much further than you expect.

Most Bourdon tube Vacuum gauges are also calibrated in inches of Mercury (typical 0 - 30"Hg) or the metric equivalent.

Getting back to balancing a set of carbs you don't need such a large scale because you are comparing the vacuums in one manifold to the vacuum in another, (differential pressure) 2 or 3"Hg would be plenty. I use a simple "U" tube about 3 ft tall filled with oil S.G. ~0.8 If I wanted to measure the Vacuum I would need it over 500 inches tall.

I was used to using mercury manometers in an instrument shop setting, they are great where you need a very accurate low pressure up to about 20 psi but they are very easy to spill.
Flour of Sulphur can be used to clean up a mercury spill, it amalgamates and allows it to be swept up.

Mercury can also have an adverse effect on Aluminium as this demonstration shows/
https://www.youtube.com/watch?v=IrdYueB9pY4

[Kiwi_Roy]

Here you go 

https://www.youtube.com/watch?v=1j-rWz-RmBo

[wirespokes]

Hey, what a hoot! Thanks Roy.

[Cdn850T5NT]

So, using my four column Motion Pro mercury containing manometer (with small orifices in ea. of the tubes... to dampen the responses of the respective mercury columns) the right process is:

- ensure that both heads are up to torque, properly;
- ensure that valves are adjusted;
- ensure that ignition system is healthy, and timed properly... LHS and RHS advance track together properly.
- remove the screw from ea. intake manifold and fit replacement screws with nipples on them to fit manometer hose;
- fit temporary caps onto the respective nipples;
- check to see that there is play in the starting circuit cables... and that there is play in ea. of the two throttle cables (play evident at the carbs).
- warm up bike by riding;
- set up fans to provide cylinder cooling;
- with bike running, in turn, fit one of the hoses to connect the manometer... one onto ea. intake manifold nipple.  Two mercury columns remain un-used... and these are set into the "closed" position on the manometer body.  Manometer body in general is set to VENT;
- do NOT rev-up /blip throttle on bike with the manometer attached;
- adjust the respective mixture screws for ea. carb to get to max idle speed... and go a wee bit richer (in deference to keeping this aircooled bike a bit cooler);
- adjust idle speed in both carbs... one at a time.  For my PHF 30 carbs, do NOT simply turn the srew against the slides.  Rather, raise the rpm a wee bit and while raised... screw-in or screw-out the idle speed screw of ea. carb to adjust, to get to equal columns of mercury between the two cylinders with no throttle-grip applied;
- finally, note that a slight application of throttle results in both columns of mercury moving together...  not one first, trailed by the other.  That adjustment is effected by the the cable terminal adjustment... locknut and cable-end.  Ensure that locking the locknut does not change the manometer results!

Do I have this right?

[Kiwi_Roy]

Do I have this right?

Yes I think so, from idle to say 2000 revs the mercury columns should stay relatively equal but don't worry about a fraction of an inch, it's just about getting the cylinders to share the load.

Manometer body in general is set to VENT; I assume you are referring to the valve to each manifold is open, both sides of the manometer and the reservoir should be under vacuum otherwise you could suck mercury into the motor

[Cdn850T5NT]

Manometer body in general is set to VENT;[/color] I assume you are referring to the valve to each manifold is open, both sides of the manometer and the reservoir should be under vacuum otherwise you could suck mercury into the motor

The Motion Pro mercury filled manometer comprises a plastic reservoir, into which four plastic-encased glass columns are affixed (at the top).  Said glass columns go to the bottom, or well-nigh to the bottom of the plastic reservoir.  At the top of each, a rubber tube is attached... and if memory serves, there is an orifice that fits into the rubber tube, there... (or the orifice is in the rubber tube, at the other end... where it attaches to the bike's manifold.  There are four rubber tubes, four columns.  When the hose is NOT used, at the top of the Motion Pro device there are "nipples" where the un-used hoses plug-in to... so that the mercury does not evaporate-away (which is hazardous).  The reservoir, below, has a short hose off the top of the reservoir, and it plugs-in to an air-tight nipple nearby, or a vent-type nipple nearby - which allows the top of the reservoir to be vented to atmosphere when in use.

So, the way I use the device... is the two unused hoses / columns remain attached to the no-vent nipples at the top of the device.  The vent on the reservoir gets shifted from Air Tight to Vented to Atmosphere... and the two intended-to-be-used columns / hoses are put onto the manifolds... ONLY once the bike is started-up, warmed up, etc....  At the last moment the manifold-plugs are removed and the hoses are attached.... so as to NOT lose the mercury into the bike's intake tract!  No blipping of throttles when attached!

[Kiwi_Roy]

The Motion Pro mercury filled manometer comprises a plastic reservoir, into which four plastic-encased glass columns are affixed (at the top).  Said glass columns go to the bottom, or well-nigh to the bottom of the plastic reservoir.  At the top of each, a rubber tube is attached... and if memory serves, there is an orifice that fits into the rubber tube, there... (or the orifice is in the rubber tube, at the other end... where it attaches to the bike's manifold.  There are four rubber tubes, four columns.  When the hose is NOT used, at the top of the Motion Pro device there are "nipples" where the un-used hoses plug-in to... so that the mercury does not evaporate-away (which is hazardous).  The reservoir, below, has a short hose off the top of the reservoir, and it plugs-in to an air-tight nipple nearby, or a vent-type nipple nearby - which allows the top of the reservoir to be vented to atmosphere when in use.

So, the way I use the device... is the two unused hoses / columns remain attached to the no-vent nipples at the top of the device.  The vent on the reservoir gets shifted from Air Tight to Vented to Atmosphere... and the two intended-to-be-used columns / hoses are put onto the manifolds... ONLY once the bike is started-up, warmed up, etc....  At the last moment the manifold-plugs are removed and the hoses are attached.... so as to NOT lose the mercury into the bike's intake tract!  No blipping of throttles when attached!

Thanks for the description, so you really have 4 individual vacuum gauges with a common reservoir, the glasses must be quite tall since each column is referenced to atmosphere.
The restriction in the hoses is so that if you suddenly apply the vacuum the mercury doesn't rush up the tube well past where it would normally sit and spill out the top, don't ask me how I know.
Many of the industrial ones have a catch pot or a cork valve that slams shut and they are vented outside.

One way to stop the mercury from evaporating is to put a drop of oil on the surface but its ok if you just keep it closed off

[Perazzimx14]

For anyone wanting to try the Corona beer bottles here's a good demo
https://www.youtube.com/watch?v=7D_f05_a74Y
I use a "U" tube manometer filled with engine oil myself but I would give this a try for sure. its compact and self standing.
One thing you might want to do on a Guzzi is finish your hoses off with a short length of rubber otherwise they fall off the nipple when it gets hot.

The guy making the video forgot to mention if using Corona bottles the 1st thing you do is find the nearest serwer and dump out the contents.

[gearman]

I said that in my OP.

[Cdn850T5NT]

Thanks for the description, so you really have 4 individual vacuum gauges with a common reservoir, the glasses must be quite tall since each column is referenced to atmosphere.
The restriction in the hoses is so that if you suddenly apply the vacuum the mercury doesn't rush up the tube well past where it would normally sit and spill out the top, don't ask me how I know.
Many of the industrial ones have a catch pot or a cork valve that slams shut and they are vented outside.

One way to stop the mercury from evaporating is to put a drop of oil on the surface but its ok if you just keep it closed off

The last time I used my manometer set (and indeed, the last few times I used it) I found that their were "gaps" in the columns of mercury... and those gaps varied as to location.  They affect the reading accuracy no doubt. It was suggested to me that somehow fuel/gasoline had made its way down the rubber tubes and therefore down some of the glass columns... and it was trapped in the columns... floating on the surface of the Hg when the manometer was not used. In use I have to wonder why or how these slugs of condensate / gasoline could show in the tubes as below some Hg that was higher-up in tube... ? In any case it was suggested to properly "condition" the device for use... one would tilt it over somewhat and in turn for ea. column, take a full 50cc syringe, full of air, and inject that air thru the rubber tube, to bubble to the top of the reservoir. To make this easier you tilt over the column to reduce the head of Hg.  This should bubble any impurities of fuel etc out of ea. column.

All: have any of you experienced this? Is my purge process correct?

[wirespokes]

I had the same problems with mine - bubbles in the columns. Got a twinmax and the mercury gauge has collected dust ever since. I'm going to try the corona manometer and compare against the electronic. That oughta be interesting.

[wicks]

If you're using a carbtune make sure to put the restrictors into the tubes else reading it will be far less accurate.

[normzone]

We used to use mercury in the instrument shops because but it's pretty much banned as being too dangerous nowadays.
Spilling a mercury manometer in your garage would be considered a major environmental disaster these days.

I used to synch my H2 (three carbs) by sticking nails or pencils under the slides and opening the throttle slowly while watching. Not bragging, just establishing a baseline for further assessments of my competency.

And I loaned my store-bought carb-synch tool to a friend who got carried away with the throttle and sucked the mercury into his engine.

[Kiwi_Roy]

I used to synch my H2 (three carbs) by sticking nails or pencils under the slides and opening the throttle slowly while watching. Not bragging, just establishing a baseline for further assessments of my competency.

And I loaned my store-bought carb-synch tool to a friend who got carried away with the throttle and sucked the mercury into his engine.

I use that method on my 72 Eldorado, it has no taps for a manometer

Oh dear, I hope he was outside.

If you read through your local work safe regulations regarding Mercury it will put you off using it.

[KiwiKev]

I use that method on my 72 Eldorado, it has no taps for a manometer

Oh dear, I hope he was outside.

If you read through your local work safe regulations regarding Mercury it will put you off using it.

We used to play with it when we were kids , maybe that explains a lot ??

Lead too for that matter, kids are wrapped up in cotton wool these days !!

[Cdn850T5NT]

I had the same problems with mine - bubbles in the columns. Got a twinmax and the mercury gauge has collected dust ever since. I'm going to try the corona manometer and compare against the electronic. That oughta be interesting.

Can anyone suggest a sure-fire method to i) clean out (what we think is) gasoline liquid / vapour "bubbles" / gaps in the mercury column; and ii) KEEP said gasoline from getting-in to the piping / columns in the first place?

With all of the necessary cautions in dealing with mercury, I imagine you could pour-out (from the reservoir) the mercury and you might be able to strain it through some panty-hose / womens' nylons.  You obviously are not straining-out gasoline... but there may be other contaminants that are not liquids.  And then, possibly, the gasoline could either leave a varnish (as it flashes-off, or as it "spoils") on the inside of the glass tubes: you could buy a super-long pipe cleaner... to rod-out the columns????  Or a really small diameter wooden dowel... and a rag on same?  You would NOT want to lose the rag down the tube, though!  What kind of cleaning solvent could aid in cleaning-out the bores of the tubes (bearing in mind that the reservoir itself is plastic - not sure what type, possibly polystyrene?)?  If you use the air-in-the-syringe trick to push-out the gasoline, get it to FLOAT on the top of the mercury.... do you even NEED to clean out the bores of the glass tubes?

Do any of you have suggestions.  I know that per the post, above, I am NOT the only person experiencing these "bubbles" / gaps in the mercury columns.  I have to wonder HOW, with mercury about 15 times more dense than gasoline... HOW it could happily sit ABOVE the gap or bubble?  It seems so implausible to me.

I want to save $ (and I like the theoretical accuracy of the Hg columns) - but I know that with bubbles in the columns, they are NOT accurate.

TIA!

[Wayne Orwig]

Can anyone suggest a sure-fire method to i) clean out (what we think is) gasoline liquid / vapour "bubbles" / gaps in the mercury column; and ii) KEEP said gasoline from getting-in to the piping / columns in the first place?

I was told by more than one person, that if you put it under a vacuum for a while all would be right again.
i sealed mine up and used my vacuum pump. Left it that way for a few weeks. It never did clear up.

[Cdn850T5NT]

I was told by more than one person, that if you put it under a vacuum for a while all would be right again.
i sealed mine up and used my vacuum pump. Left it that way for a few weeks. It never did clear up.

Wow... amazed that the stuff is so hard to get rid of!

[Cdn850T5NT]

Can anyone suggest a sure-fire method to i) clean out (what we think is) gasoline liquid / vapour "bubbles" / gaps in the mercury column; and ii) KEEP said gasoline from getting-in to the piping / columns in the first place?

With all of the necessary cautions in dealing with mercury, I imagine you could pour-out (from the reservoir) the mercury and you might be able to strain it through some panty-hose / womens' nylons.  You obviously are not straining-out gasoline... but there may be other contaminants that are not liquids.  And then, possibly, the gasoline could either leave a varnish (as it flashes-off, or as it "spoils") on the inside of the glass tubes: you could buy a super-long pipe cleaner... to rod-out the columns????  Or a really small diameter wooden dowel... and a rag on same?  You would NOT want to lose the rag down the tube, though!  What kind of cleaning solvent could aid in cleaning-out the bores of the tubes (bearing in mind that the reservoir itself is plastic - not sure what type, possibly polystyrene?)?  If you use the air-in-the-syringe trick to push-out the gasoline, get it to FLOAT on the top of the mercury.... do you even NEED to clean out the bores of the glass tubes?

Do any of you have suggestions.  I know that per the post, above, I am NOT the only person experiencing these "bubbles" / gaps in the mercury columns.  I have to wonder HOW, with mercury about 15 times more dense than gasoline... HOW it could happily sit ABOVE the gap or bubble?  It seems so implausible to me.

I want to save $ (and I like the theoretical accuracy of the Hg columns) - but I know that with bubbles in the columns, they are NOT accurate.

I suppose you could test-out your cleaning success by using a MityVac on it... to see that the columns remain gap-free.

TIA!

[Cdn850T5NT]

Sorry, I "quoted" rather than "Modified".

[larrys]

Can anyone suggest a sure-fire method to i) clean out (what we think is) gasoline liquid / vapour "bubbles" / gaps in the mercury column; and ii) KEEP said gasoline from getting-in to the piping / columns in the first place?

With all of the necessary cautions in dealing with mercury, I imagine you could pour-out (from the reservoir) the mercury and you might be able to strain it through some panty-hose / womens' nylons.  You obviously are not straining-out gasoline... but there may be other contaminants that are not liquids.  And then, possibly, the gasoline could either leave a varnish (as it flashes-off, or as it "spoils") on the inside of the glass tubes: you could buy a super-long pipe cleaner... to rod-out the columns????  Or a really small diameter wooden dowel... and a rag on same?  You would NOT want to lose the rag down the tube, though!  What kind of cleaning solvent could aid in cleaning-out the bores of the tubes (bearing in mind that the reservoir itself is plastic - not sure what type, possibly polystyrene?)?  If you use the air-in-the-syringe trick to push-out the gasoline, get it to FLOAT on the top of the mercury.... do you even NEED to clean out the bores of the glass tubes?

Do any of you have suggestions.  I know that per the post, above, I am NOT the only person experiencing these "bubbles" / gaps in the mercury columns.  I have to wonder HOW, with mercury about 15 times more dense than gasoline... HOW it could happily sit ABOVE the gap or bubble?  It seems so implausible to me.

I want to save $ (and I like the theoretical accuracy of the Hg columns) - but I know that with bubbles in the columns, they are NOT accurate.

TIA!

I had the same problem with my mercury sticks. I blew in the hose to push all of the mercury out of the affected tube into the reservoir. When you stop blowing the mercury reenters the tube sans bubbles. Might take a couple tries. Do not suck on the hose! YMMV.
Larry

[Cdn850T5NT]

Thank you, LarryS.

I will give it a try...

Cheers!

[wirespokes]

I emptied and refilled mine. Worked for a while then got bubbles again. I got tired of fussing with it. Not worth the trouble. In the time I spent trying to get it to work right I could have made twenty beer bottle balancers and ridden half way across the country. On top of all that, it's mercury - the stuff evaporates, silly as that seems, so you have to ensure it's closed to atmosphere when you're done using it. It's a dangerous substance so that that into consideration. I know, an electronic balancer costs some bucks, but here we've got the perfect guzzi tool for an incredibly low price (guzzi content), so it should be a no-brainer tossing the mercury stix and moving up to the bbb (beer bottle balancer).

I know I would if I was in your position.

[Cdn850T5NT]

Just found the solution to the bubble issue... if a person did want to keep the mercury manometer based tool:  http://gpzweb.s3-website-us-east-1.amazonaws.com/ManometerNotes/ManometerNotes.html  It seems to me that the mercury sticks give an immediate indication of which carb (slide) starts to open first... that the beer bottle manometer does not.  In any case, ideally, the beer bottle device and the mercury manometer could both be used, i.e. simultaneously.

The trick is to collapse the Hg columns using a syringe each time you use the device... while it is hooked up and the engine is running.  A simple pull on the syringe (applied to the vent tube) does the trick for each tuning session.

See the link above, plus the two photos



 provided (from the article).

The device in the cited article is, in fact, a Motion Pro manometer...

[Cdn850T5NT]

And, amazingly, here is a source for mercury if you need it:  https://www.saber-cycle.com/store/product1003.html

AMAZING that they still have this.

[Kiwi_Roy]

And, amazingly, here is a source for mercury if you need it:  https://www.saber-cycle.com/store/product1003.html

AMAZING that they still have this.

It's quite expensive, 70 grams would be 5 cc (maximum quantity they can post), definitely worth it if you were just a little shy
I worked for a firm that spent millions of dollars trying to rid the town of Squamish of mercury spilt from an old Chlorate plant, it was used as one electrode in an electrochemical cell, we ran a plant for about 5 years to remove a few Kg from the groundwater