Kawasaki Concours Forum
The C-14, aka Kawasaki Concours-14, the new one :) => The Bike - C14/GTR 1400 => Topic started by: B.D.F. on September 21, 2011, 02:53:32 PM
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I just finished doing the second T.B. synch. on my bike at 73K miles- the one previously had been done at just over 50K miles. Both times the center balance screw between the two sets of throttle bodies (the screw between T.B. #2 and #3) was off considerably. The first time I balanced the TB's there was no noticeable difference afterward but they were not all that far off to begin with- they were w/in 2 cm of mercury before I started if I remember correctly. This time they varied by close to 4 cm and the bike had been running a bit poorly; an increase in vibration, especially on initially opening the throttle, slugging acceleration when using small throttle openings and longer cranking times. I also had to adjust the air bleed screws on T.B. #1 and 2 but those were not off much by comparison (less than 1 cm on #1 and #2) This time the difference was immediately noticeable- throttle response greatly improved, and vibration is down by quite a bit.
It seems that the joint in the middle of the throttle linkage may be a wear point. Of course I do not know if this is just on my bike or is something in the design that will cause it to change over time on most (or all) C-14's but it is probably worth a check on any high mileage bikes. It is easiest to combine the T.B. synch with a valve lash check, spark plug change and air filter change or inspection because it is a fair amount of work to do the T.B. synch alone. Combining it with other maintenance items at least shares a lot of the labor with other engine maintenance tasks.
Brian
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I am puzzled about my TB sync, first one done at about 55,000 miles. The idle smoothed out quite a bit and low speed vibration gone. But it now takes a little longer to warm up, the same thing I experienced at high altitude last summer in Taos (6000+ft) I also find that the idle speed is inconsistent with varying temperature now where it was always contant before the sync.
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... increase in vibration, ...
... slugging acceleration when using small throttle openings ...
These are symptoms I've had with my bike from the first day of ownership. My dealer recommended a TB sync to Kawasaki within the first couple of months, but they would not authorize it. Now, after 21,000 miles, it's no better.
Thanks for providing this information, as it reinforces my hope that a TB sync will make my bike better. It's just the damn annoyance of buying a new bike so I would not have to work on it, only to be put into this scenario that frustrates me so.
I have not bought a gauge set yet, and at this point, I don't trust *any* dealer to do it right. As soon as I find the time to do some shopping, I'll have a TB sync gauge set, and I'll tackle this job (during the upcoming wet season). If anyone has recommendations on their favorite gauge set and why you like it, please feel free to let me know.
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Seeing as you ask- I am a big fan of mercury manometers because they work on physics and not only do not require calibration / adjustment of any kind but they cannot be misused or affected by anything anyone might do to the gauges other than to possibly have a loose vacuum connection, which would defeat any vacuum gauge. I don't know if they are even available anymore. The newer Motion Pro liquid gauges do not seem to have a big fan base but I have not used them so will not comment beyond that. The ones from England (cannot remember the name) with the metal slugs in the tubes should be OK as long as they are checked to make sure they all read the same value with one vacuum source before they are used.
There was a lot of info. on the old forum about this but seeing as that is long gone, please be aware that a T.B. synch. is a fairly frustrating job on this bike. It is not particularly difficult but it takes a lot of effort to get a mirror, light source and a tool into the recess behind the T.B. and actually move the adjusting screws. You cannot even see them without a mirror, let alone get a tool anywhere near them. Also the vacuum caps on the T.B. themselves can be pesky, especially #2, so I recommend stringing vacuum lines to the left side of the bike and then leaving them there permanently. That way you only have to run the vacuum lines one time. Mark each one as to which T.B. it is attached to, cap the ends when done so there are no vacuum leaks and then just tie- wrap them to a frame member well away from the throttle mechanism. Should you do a T.B. synch a second time you will really appreciate this.
I believe a fantastic tool to use on this job would be one of the flexible bore scope, LCD packages. That would put a camera and lighting on the screw you are trying to reach so at least you could see when you missed the screw. Store up a few extra nasty words too 'cause you might need them.
I would suggest doing a T.B. synch with other engine maintenance such as a spark plug change and valve lash check so at least the labor of getting to those various areas is divided amount several different jobs. Put another way, the underlying labor is almost the same to get to all of those tasks so it is easy to combine them.
Brian
... increase in vibration, ...
... slugging acceleration when using small throttle openings ...
These are symptoms I've had with my bike from the first day of ownership. My dealer recommended a TB sync to Kawasaki within the first couple of months, but they would not authorize it. Now, after 21,000 miles, it's no better.
Thanks for providing this information, as it reinforces my hope that a TB sync will make my bike better. It's just the damn annoyance of buying a new bike so I would not have to work on it, only to be put into this scenario that frustrates me so.
I have not bought a gauge set yet, and at this point, I don't trust *any* dealer to do it right. As soon as I find the time to do some shopping, I'll have a TB sync gauge set, and I'll tackle this job (during the upcoming wet season). If anyone has recommendations on their favorite gauge set and why you like it, please feel free to let me know.
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Get Fred's videos.
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I have experience with the Motion Pro and the Morgan Carbtune. IMO the Motion Pro is unuseable junk, at least the one I have. It requires calibration before each use but all my attempts to calibrate resulted in the fluid becoming filled with air gaps. The adjustments screws would not rotate smoothly as if the threads were not properly formed. Maybe I just had a bad unit. I gave up on it and orferd the Morgan Carbtune Pro the one with the metal "slugs". It worked well and was easy to use.
I found a large rectangular mirror on a stick and this made the job a lot easier. It took a lot of trial and error to get the mirror and flashlite positions just right and secured but once that was done the actual adjusting was not too bad. The center screw WAS quite a challenge, I had to practice a while to teach my eyes/brain how to work backwards.
I did use Fred's video and it was helpful. Connecting the number 2 hose was a PIA Fred's way but you don't have to remove the fuel tank, just prop it up.
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I would love to find an old mercury based one, but they are rare. I'm planning to do the TB sync right after / while doing the valve adjust. I have inspection mirrors and tools for reaching into tight places, so all should be good there. Also planning to add remote hoses for future syncs.
Lather, I remember how much fun you had with the anti-freeze based unit. The slug style is the likely candidate, unless I can find a mercury based one.
Are these three the only real choice, other than dial gauges (not really a good choice though)?
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Brian, I seem to remember a post From you a while back discussing it being acceptable to balance with the individual bleed screws and bypass the center screw all together. That's how I did mine. Forgive me if I misquote. If I did, can you refresh my memory? When I pulled maintenance, I just set them all to highest value the bodies would produce on the carbtune and then tapered them all down to match the lowest value.
Also, I've got my hoses coiled up and stored for future use on right side versus left. I capped them good with electrical tape. I noticed from ur post u advocated left side. Does it matter? If so I need to crack the Tupperware and move ASAP.
As always, appreciate your advice.
Will
I just finished doing the second T.B. synch. on my bike at 73K miles- the one previously had been done at just over 50K miles. Both times the center balance screw between the two sets of throttle bodies (the screw between T.B. #2 and #3) was off considerably. The first time I balanced the TB's there was no noticeable difference afterward but they were not all that far off to begin with- they were w/in 2 cm of mercury before I started if I remember correctly. This time they varied by close to 4 cm and the bike had been running a bit poorly; an increase in vibration, especially on initially opening the throttle, slugging acceleration when using small throttle openings and longer cranking times. I also had to adjust the air bleed screws on T.B. #1 and 2 but those were not off much by comparison (less than 1 cm on #1 and #2) This time the difference was immediately noticeable- throttle response greatly improved, and vibration is down by quite a bit.
It seems that the joint in the middle of the throttle linkage may be a wear point. Of course I do not know if this is just on my bike or is something in the design that will cause it to change over time on most (or all) C-14's but it is probably worth a check on any high mileage bikes. It is easiest to combine the T.B. synch with a valve lash check, spark plug change and air filter change or inspection because it is a fair amount of work to do the T.B. synch alone. Combining it with other maintenance items at least shares a lot of the labor with other engine maintenance tasks.
Brian
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I have that camera with the flexable shaft and it works great to get into that tight space to see and adjust that TB screw.
I got it at Harbor Freight for 120.00 but now it's at 80.00 and I've seen it at 70.00.
The extra long needle nose pliers from HF works well at removing the vacuum cap on #2 cylinder
I made up a mounting block for the vacuum lines. Keeps things neet and easy the next time the job needs to be done
Bill
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I do not remember making that post but I believe you can make all adjustments using just the bleed screws provided that there is not much adjustment needed and that none of the bleed screws are at or very close to the [min. or max] adjustment already.
The situation I found on my bike twice now was a significant amount of difference between the two sets of T.B.'s connected via the adjustment in the linkage. It was pretty obvious that either something in that connection had moved or some wear had taken place. It is not really possible to compensate for that with the air bleed screws because the throttle openings of each T.B. are different and the air bleed screws can only be set to compensate at one engine speed. The true correction is to again rebalance the throttle openings themselves by using the adjustment in the linkage provided (the linkage or mechanical balance adjustment screw).
This whole thing highlights another problem whenever using the air bleed screws to make any adjustment(s): they have a limit as to how much they can be adjusted in either direction, both more and less open. There is no easy way that I know of to tell where the screws start off so one or more may be close or at the limit of adjustment when starting the balance. I do not know if the manual makes provisions for that condition or not but the only way around it that I can think of would be to stop the engine and move all the screws back to some neutral starting point such as one or one and a half turns open from fully closed (the ideal spot would be 1/2 way between fully closed and fully open but I don't know what the travel range really is).
Back to which adjustment to use: if there is a clear difference between the throttle bodies in the pairs 1 & 2 and 3 & 4, then that difference should be taken out with the mechanical balance screw. Any individual T.B. imbalances can then be changed using the air bleed screws. To be more specific, the average of 1 & 2 and the average of 3 & 4 should be the same by adjusting the linkage screw and then the individual air bleed screws adjusted.
Brian
Brian, I seem to remember a post From you a while back discussing it being acceptable to balance with the individual bleed screws and bypass the center screw all together. That's how I did mine. Forgive me if I misquote. If I did, can you refresh my memory? When I pulled maintenance, I just set them all to highest value the bodies would produce on the carbtune and then tapered them all down to match the lowest value.
Also, I've got my hoses coiled up and stored for future use on right side versus left. I capped them good with electrical tape. I noticed from ur post u advocated left side. Does it matter? If so I need to crack the Tupperware and move ASAP.
As always, appreciate your advice.
Will
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Brian, thx...what about where to leave the hoses for future use...left side or right side? I've currently got coiled up to the right.
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It does not matter where the hoses terminate as long as you can get to them easily. I guess the right side would be a tad safer because the throttle linkage is on the left side and a loose hose could get tangled there. ?? Mine are on the left side but only because that is the side I adjust the the T.B.s from. As long as they are capped or plugged and do not rub against anything all should be fine.
Brian
Brian, thx...what about where to leave the hoses for future use...left side or right side? I've currently got coiled up to the right.
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Are these three the only real choice, other than dial gauges (not really a good choice though)?
no, they are the choices everyone makes based on cost and percieved accuracy.
If you truley want the best SYNCH tool, (notice i am not saying tool to get an actual reading on vacume), the best by a long shot is the Twin-Max..I have tested it up against every current gauge out there, and none were as accurate or sensitive in "comparative synching", which is what you are doing, comparing A to B.
http://www.aerostich.com/twinmax-synchronizer.html (http://www.aerostich.com/twinmax-synchronizer.html)
just for reference, you can find them cheaper, you have to look around, I paid $79 for mine 6 years ago.
the hoses on my kawasaki issued mercury sticks (I bought in 1975) are gonna rot before I ever use that tool again.
The Twin-Max, coupled with a single accurate calibrated vacume gauge (to find the actual vacume for the comparison start point, i.e. actual mm/hg) are the best combo.
this works;
http://tiny.cc/lax6p (http://tiny.cc/lax6p)
you only need one....
mind you, I have installed hoses that reside on the left side of the bike also, plugged, been there since I adjusted valves the first time.
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no, they are the choices everyone makes based on cost and percieved accuracy.
If you truley want the best SYNCH tool, (notice i am not saying tool to get an actual reading on vacume), the best by a long shot is the Twin-Max..I have tested it up against every current gauge out there, and none were as accurate or sensitive in "comparative synching", which is what you are doing, comparing A to B.
http://www.aerostich.com/twinmax-synchronizer.html (http://www.aerostich.com/twinmax-synchronizer.html)
just for reference, you can find them cheaper, you have to look around, I paid $79 for mine 6 years ago.
the hoses on my kawasaki issued mercury sticks (I bought in 1975) are gonna rot before I ever use that tool again.
The Twin-Max, coupled with a single accurate calibrated vacume gauge (to find the actual vacume for the comparison start point, i.e. actual mm/hg) are the best combo.
this works;
http://tiny.cc/lax6p (http://tiny.cc/lax6p)
you only need one....
mind you, I have installed hoses that reside on the left side of the bike also, plugged, been there since I adjusted valves the first time.
Thanks MOB,
I was searching around for a good price on the TwinMax, and found this drawing on a BMW site: (http://img370.imageshack.us/img370/8247/manometersketch15by.jpg).
First thing I thought was "Now that's the ultimate Connie owners TB sync tool!" ;)
For those who are interested, here is the thread it came from, with pics of it in use: http://www.bikersoracle.com/rs/forum/showthread.php?t=1910 (http://www.bikersoracle.com/rs/forum/showthread.php?t=1910)
I just know I'll have to try this, for curiosities sake. ::)
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Just one more time before you start: I think it is a bad idea to try to balance more cylinders than you have individual manometers for. As you change one vacuum setting, the other cylinders will change but you will only be able to view one at a time. When you change the air passing through each throttle body, the idle will change as will the power output from that cylinder thereby changing all the other cylinder’s vacuum reading. This is quite obvious when you use a four tube manometer to balance a four cylinder engine; each small tweak changes all four cylinder’s throttle body’s vacuum. I am not saying it cannot be done, I am saying that using a pair on manometers on a four cylinder engine makes the process much harder and very potentially less accurate than it has to be.
The sketch you have there is not be a manometer per se, it is a balance gauge. It will work just fine but it will be difficult to quantify the difference in vacuum between ports. You can expand that basic design to accommodate more cylinders though by using a common tube at the bottom, then coming straight up with as many tubes connected to that bottom tube as you have cylinders. So one cross- tube across the bottom coupled with two tees and two elbows allowing four tubes to run straight up will work for a four cylinder engine. Use something that will pass safely through the engine such as transmission fluid and it is worth a try. The physics of the pressure differential will absolutely work but I cannot tell you how close each tube has to be to the average to be 'in spec.' because again that is a differential gauge, not a manometer that can be calibrated according to the material used as the fluid only.
Brian
Thanks MOB,
I was searching around for a good price on the TwinMax, and found this drawing on a BMW site: (http://img370.imageshack.us/img370/8247/manometersketch15by.jpg).
First thing I thought was "Now that's the ultimate Connie owners TB sync tool!" ;)
For those who are interested, here is the thread it came from, with pics of it in use: http://www.bikersoracle.com/rs/forum/showthread.php?t=1910 (http://www.bikersoracle.com/rs/forum/showthread.php?t=1910)
I just know I'll have to try this, for curiosities sake. ::)
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Well sure it's only a balance guage, but you could make 3 of them, connect them all up at the same time, and then you would have a compound (complex?) balance gauge. ;)
Come on Brian, where's that sense of Yankee Enginuity! ;D
Good thing you ride a C14, you would never pass for a C10 rider. ::)
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Er, well I already addressed that. You can have as many cylinders on ONE gauge as you want just by using Tees cut into the line at the bottom. That way you don't have to worry about having the identical amount of fluid in each gauge nor if each one is at the exact same height.
C'mon, physics is your friend.... and you don't want it to be your enemy because that almost never goes well. :o
Brian
Well sure it's only a balance guage, but you could make 3 of them, connect them all up at the same time, and then you would have a compound (complex?) balance gauge. ;)
Come on Brian, where's that sense of Yankee Enginuity! ;D
Good thing you ride a C14, you would never pass for a C10 rider. ::)
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Slightly confused here,
Fred's video shows adjusting the center screw that balances the left /right banks BEFORE you sync the banks... Wouldn't it be better the other way around? (Sync the left 2 carbs to each other, then sync the right 2 carbs to each other then match them with the center screw?)
*scratches head*
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Er, well I already addressed that. You can have as many cylinders on ONE gauge as you want just by using Tees cut into the line at the bottom. That way you don't have to worry about having the identical amount of fluid in each gauge nor if each one is at the exact same height.
C'mon, physics is your friend.... and you don't want it to be your enemy because that almost never goes well. :o
Brian
OK, fair enough, though your suggestion only covered the bottom half of the problem. There would also need to be restricted equalization tube connections at the top. Ideally, if it had a adjustable restriction (using a thumb screw), then it could be used to adjust the sensitivity as balance was dialed in.
I know it's not a Manometer, but with adjustable sensitivity, it would probably provide for a very accurate synch.
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Slightly confused here,
Fred's video shows adjusting the center screw that balances the left /right banks BEFORE you sync the banks... Wouldn't it be better the other way around? (Sync the left 2 carbs to each other, then sync the right 2 carbs to each other then match them with the center screw?)
*scratches head*
Per the FSM on page 2-19, you are correct. It states to do 1 & 2, 3 & 4, then the left & right halves.
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I have not see the videos but I would not do it the way you are suggesting because there will be significant changes between each T.B. on each side (in other words, the relationship between T.B. #1 and 2, and T.B. #3 and 4) will change as the balance screw is changed.
Here is how I do it: first note all levels on the manometers. What we are really after here is the difference, not an absolute reading. So suppose you find the following:
#1: 230 mm Hg
#2: 250 mm Hg
#3: 260 mm Hg
#4: 270 mm Hg
First, average #1 and 2 and #3 and 4 like this: the averages of 1& 2 is 240 mm Hg, the averages of #3 and 4 is 265 mm Hg. The mechanical balance screw is between cylinders #2 and #3 and changes the relationship between the opening angle of the throttle plates. So move that balance screw until the averages of #1 and 2 equal the averages of #3 and #4. Now maybe the new readings are:
#1: 245 mm Hg
#2: 255 mm Hg
#3: 240 mm Hg
#4: 260 mm Hg
Now adjust the air bleed screws on each throttle body. The manual states to increase the lower vacuum of each set to the higher vacuum of each set (a set being either #1 and #2 or #3 and #4). This is fine.... if it works. I tend to adjust mine both up and down as required so as not to be turning the screws in all the time. Either way, balance all the T.B.'s using the air bleed screws until they are reasonably close to the same- reasonable being at least w/in 10 mm, and better yet w/in 5 mm of each other.
NOTE: at some point, if the air bleed screws are always turned in to always increase the lower cylinder vacuum, the screw will eventually seat and no longer be adjustable. If (when) that happens, something needs to be done to reset all the air bleed screws to some neutral point: I would suggest something like two turns from the fully closed position or each air bleed screw which should be a decent starting point. After the reset, the synch. will need to be done again. Sorry, there is no way out of this that I know of other than not screwing in all the screws for every adjustment, and that is not a guarantee either.
Brian
Edited to make all measurements in mm; some were in cm and some were in mm.
Slightly confused here,
Fred's video shows adjusting the center screw that balances the left /right banks BEFORE you sync the banks... Wouldn't it be better the other way around? (Sync the left 2 carbs to each other, then sync the right 2 carbs to each other then match them with the center screw?)
*scratches head*
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Yeah, you could use some type of adjustable restrictor but I would steer away from any more adjustments than necessary. Solid restrictors are the better way to do IMO and you can probably get them from some place like Motion Pro for a few dollars. Besides all of that, the C-14 has restrictors built into the venturi tubes so I do not think the external ones normally used are even needed on this bike.
The problem with the balance meter is that you have no idea what 1/2" difference between cylinders means- is that very close or too far apart? Another beautiful thing about mercury manometers is that physics controls the height of the mercury and it is easy to quantify the height (in any length units you want).
Again, I am pretty confident that a "4- banger" vacuum balancing tool with a common manifold on the bottom and using something like ATF would work fine, but it would be best to calibrate the difference in the liquid height(s) as it compares with something known like inches of water or mm of mercury (in* H20 or mm* Hg). Once that is done you could scratch in onto the plank that holds the tubing for all time- something like 1" H2O = 5" Hg so that future generations will know what you were trying to do when they find that thing in an archival dig.... ;D Seriously, the physics of the balance gauge will work fine, and I am a fan of home made tools (or tools used for the 'wrong' purpose like spark plug sockets to remove front axle bolts) but this will require a bit of tinkering and study to get it to be useful IMO. Best of luck and please do let us know how you make out.
Brian
OK, fair enough, though your suggestion only covered the bottom half of the problem. There would also need to be restricted equalization tube connections at the top. Ideally, if it had a adjustable restriction (using a thumb screw), then it could be used to adjust the sensitivity as balance was dialed in.
I know it's not a Manometer, but with adjustable sensitivity, it would probably provide for a very accurate synch.
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Well it's been a while since we've visited this thread, but I wanted to follow up with my test results from the homemade balance gauge. I must say, if I had known it was going to work as well as it does, I would've taken a little more pride in its construction, to make it better looking for pictures.
I had already planned out several revisions to the gauge in my head, and different fluids to try, but it wasn't necessary since it worked fantastically well first try. The gauge is very sensitive to pilot screw adjustments, as a very small change in the pilot screw has a very noticeable change on the gauge.
I bought 8 feet of 3/16ths inch clear vinyl tubing from ace hardware for $10, and a 4-way tee for $0.68. The white cardboard backing and plastic strips to tie the hoses on were free. The tubing was cut into 4 equal pieces. The fluid is just regular antifreeze.
On the bike I installed high temp red silicone 5/32" vacuum hose. This stuff is very stretchy and easily seals over the vacuum ports on the throttle bodies, as well as the 3/16" brass hose splices I used. It fits tight enough, that I didn't hassle with putting clamps over it. I put the plugs removed from the throttle bodies (and their clamps) on the end of the splices.
I used a mechanical gauge to measure the actual amount of vacuum on each cylinder. After the valve adjustments, I was not able to balance all 4 cylinders using just the pilot screws. When checking the values with the mechanical gauge, 1 and 2 where very high, almost 300mmHg.
I gave, up turned all the pilot screws all the way in, then back out 1.5 turns. I then turned the center balance adjust screw in until the left and right sides were almost equal (between 1/8 and 1/4 turn). After that the pilot screws dialed it right in. When I was done playing with the balance gauge, I checked all 4 cylinders with the mechanical gauge, and they were dead on at 260mmHg.
I made a quick video with my phone of the engine running and the balance gauge attached, however I didn't realize my phone would not rotate video like it does with still pictures. Sorry, you'll have to tilt your head to the left to watch it.
Any questions?
http://youtu.be/2BnWWgjKQpo (http://youtu.be/2BnWWgjKQpo)
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Thanks C1 for posting this!
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- ingenious !!
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I've done this method for twenty years now with carburetors:
I have tried using mercury sticks, the problem I had with it was there was no restrictions on the columns, so they bounced up and down about a cm or more with every piston cycle...tuning with them was trying to guestimate the middle point on the jumping mercury high and low point.. Even after I put line restrictors in it was still pretty bad....finally my instrument cracked when apparently it became brittle and cold...so I disposed of it in an environmentally friendly way decided to make my own.
So here's what worked best for me on my '96 GPz that I rode for over 250K miles and 20 years of tuning it, and it's super cheap: I got like 20 feet of clear plastic tubing...4 mm I guess, it's always fit on every bike I've tried it on...some zip ties and a yard stick and some ATF and you're in business. Zip tie the tubing to the front of the yard stick making a tall "U" all down it's length with like 7 feet of tails hanging off the top of each side, the closer you can get the tubes together the better without kinking the tubing. With a turkey baster or syringe, slowly and patiently put just enough ATF in the tube to come up 18 inches on each tube. Hang it vertically when you do this, and wait for at least a day after to ensure all of the ATF ends up smack dab in the center with no air bubbles...it doesn't have to be precisely 18 inches, just roughly halfway up. (More on this later)
ATF works beautifully because it seems to have just the right amount of viscosity and that wonderful red color that makes it easier to see. If it were to somehow get sucked into the vacuum port it won't cause any real harm either, just get burned up.
So synching carbs I imagine is near exactly like synching TBs. Here's why on this homemade manometer you don't have to be precise on the height: it is comparing vacuum on two cylinders against each other via the side by side column heights, not comparing vacuum on a mercury column against atmospheric pressure.
So you first synch #1 and #2 cylinders against each other, then #3 and #4, then either #1 against #4 or #2 against #3. With carbs and their common linkage there is only ever 3 adjustment screws, between carbs 1&2, 2&3, and 3&4. The screw between 2&3 adjusts both pairs of carbs 1&2 against pairs 3&4. I'd just hang my manometer off of garage ceiling right where I can see it while fiddling with the adjustment screw.
The real advantage of doing it this way, comparing only two cylinders at a time to each other, is you get far better sensitivity on the ATF manometer. For example, and this isn't exact but a guestimate to make a point, a 1mm change in height of a mercury column would be more like a 1 inch change in ATF column height....and for one column to go up one inch means the other went down an inch, so you can see two inches of difference between columns....far greater resolution so you can make much finer adjustments....and on Keihen CV carbs, this really is important, and I imagine it is with the TBs too.
The other thing is that the columns don't jump up and down with each cylinder's cycle.... there's less variation in the timing of the vacuum pulses against each other vs against an atmospheric reference pressure, and again, the ATF seems to have just enough viscosity to resist sudden movements.
The only real disadvantage is that you have to stop the bike engine and move the connections each time you are done synching two cylinders against each other, for a minimum of three iterations. (Again, #1 vs #2, #3 vs #4, and #1 vs #4.)...and there were times after a carburetor rebuild when I went through more than six iterations.
So I'm looking forward to synching my new C14 TBs here in the future. My old school manometer is well up to the challenge.
Jeff in WA
Yeah, you could use some type of adjustable restrictor but I would steer away from any more adjustments than necessary. Solid restrictors are the better way to do IMO and you can probably get them from some place like Motion Pro for a few dollars. Besides all of that, the C-14 has restrictors built into the venturi tubes so I do not think the external ones normally used are even needed on this bike.
The problem with the balance meter is that you have no idea what 1/2" difference between cylinders means- is that very close or too far apart? Another beautiful thing about mercury manometers is that physics controls the height of the mercury and it is easy to quantify the height (in any length units you want).
Again, I am pretty confident that a "4- banger" vacuum balancing tool with a common manifold on the bottom and using something like ATF would work fine, but it would be best to calibrate the difference in the liquid height(s) as it compares with something known like inches of water or mm of mercury (in* H20 or mm* Hg). Once that is done you could scratch in onto the plank that holds the tubing for all time- something like 1" H2O = 5" Hg so that future generations will know what you were trying to do when they find that thing in an archival dig.... ;D Seriously, the physics of the balance gauge will work fine, and I am a fan of home made tools (or tools used for the 'wrong' purpose like spark plug sockets to remove front axle bolts) but this will require a bit of tinkering and study to get it to be useful IMO. Best of luck and please do let us know how you make out.
Brian