How can i synchronizing xj 750 seca carburetor without carbs

How can i synchronizing xj 750 seca carburetor without carbs sync tool?
Hello everybody i'm from thailand in my country is very hard to find carbs sync tool such as motion pro whatever you named its.So i want to know its could be possible to carbs tune without the tool

 

Re: How can i synchronizing xj 750 seca carburetor without c

thanh,

Len sells one. Click on the logo in the top right corner (XJ4ever). Also....
Search > Forums > (in the top box type "Carbs Sync Tool" or "Vacuum Sync Tool") > Submit. Or go to FAQ Suggestions and look at Gamura's post for making one. Two baby bottles, two tub stops, 10' clear hose and ATF. Hope this helps.

Gary

 

I you go on youtube, you will find several videos about balancing or synchronizing your carbs with homemade devices. I like that one because I can actutally see what is going on, the only thing it doesn't show is where are the vacuum ports on the carbs:

http://www.youtube.com/watch?v=GaTRyHxvneY

That one is the cheapest you could imagine, but it is for only two carbs at a time, you would have to do it by pairs several times:

http://www.youtube.com/watch?v=ufZ_IYLG ... creen&NR=1

I also have an accurate drawing of a four-carb balancing device that is a little bit more complicated to fabricate but still simple to use, it is a pdf file, if you're interested, i'll have to figure out how to post pdf files on this site.

 

Here is the pdf file:

www.j3p.com/sabmag/synctool.pdf

I'm pretty sure it would work well without the resonators.

 

What quebecois59 posted will work without the "resonators" but you'll still want restriction. On the recommendation of RickCoMatic, I built 4 using a two hose connector, and epoxying a red tube from a can of carb cleaner. Should be cheaper than all those valves.

Note that the resonators is a fine idea for preventing the engine from sucking up the fluid, and would make filling it much easier. However, without one, you'll need to keep an eye on the fluid as soon as you start it. If one is sucking up way to much fluid, shut the bike off, coarse adjust the sync, then try again. AFT won't hurt the engine if it's burned.

Finally, pay attention to the yard stick. You'll need at least a 3 ft column for measurement, and another 3 feet of tubing to connect to the vacuum ports.

 

Did you put one restrictor for each line? I imagine that without the resonators, you'd better have longer hoses so it will give you more time to shut off the engine if needed.

 

I put one on each line.

Ithink the point of the resonators is that they have much more volume per change in height than the tubes themselves, so all of the fluid collects there and can't get siphoned off. Which was also one of the strong points for the baby bottle tool.

But they seem complicated and expensive to build.

 

THe baby bottle tool is pretty cool, actually, and I will go for it if I can find four of these rubber caps to fit snug on the bottles. The fun part is that no fluid could be sucked in the carbs at any time.

 

I can tell you from experience that the 4 tube tool is better than the baby bottle tool, because you measure pressure differential via the height of the fluid, and baby bottles simple don't have enough height. That and they don't respond quickly enough to give you a good reading.

Fluid getting sucked up isn't really a problem if:
1: you have 3ft column (necessary for measurement anyway.
2. When you first start your sync, you are ready to shut down the engine if one is drawing way too much vacuum.

If you are REALLY worried about it, that link you posted solves both the measurement and fluid siphoning problem.

 

All right, thanks for your feedback. I'm not so confident with my skills about fabricating one with resonators and valves but I'll start with one without resonators but with restrictors and see how it goes on.

I'm not quite sure though if I understand correctly how to install the red tube and the two hose connector, do you simlpy slide the redtube in the connector and glue it in place? I'm more of a visual guy, somtimes I can't figure out simple thnigs without a picture or a drawing...

 

yeah, just leave a little extra on the ends of the red tubes so you can cut it to shape and keep any glue out of the tube.

 

I can cut it to length, not to shape, i guess the shape wouldn't matter...

 

sorry...my bad, I meant "cut to length"

 

No problem!

The funny thing with this tool in the pdf is that you could use it for engines with one to four cylinders, just have to unplug from the circuit the lines you don't need.

 

Ah....that's due to the valves on top!

The pdf is wrong though, it only applies to motorcycles with 2-4 cylinders.
And you can build one for 2 cylinders with just a hose and restrictors (no need to disconnect hoses. It'll probably cost just as much to build 3 manometers than it would for those valves (I've spent a bunch of time staring at the plumbing section of Home Depot trying to justify which pieces to buy). Though I guess you'd only need 2 valves if you built in restrictors.

If you are tuning many different bikes, with many different engine configurations, it's probably best to buy the tool ;-)

 

Well, I may be wrong but I'd think that if you unplug, let's say, the 4th tube on the right, then put an 90 degrees instead of a T between 2nd and 3th at the base of the tubes, you could use the tool as is for a 3 cyl engine. It wouldn't have anything to do with the valves, though.

 

if you don't start with a good bench sync a tube device like that will drive you nuts.
you should really consider the two bottle type, no restrictors, very forgiving ,maybe more accurate and way easier and cheaper to make.

 

I agree with Polock that starting off with a good bench sync is important, but we should be doing that anyway right? I mean, if you are working at a shop where you can't be removing the carbs for every customer that comes in, then a good bench sync might not be a good assumption (and you would buy a proper tool). But for the home mechanic, that's standard operating procedure.

I've synced my carbs no problem with the 4 line tool. And I've had the sync be off enough to suck up the fluid, but stopped the engine before it did. Made a correction and started again.

If you don't know which way to turn the screws go to correct the sync, write it down. It doesn't take more than a couple of engine starts from bench sync to get into a range where the fluid won't get sucked up.

The bottle tool is no more accurate, in fact, depending on the size of the transfer tube, you can restrict the fluid flow from one bottle to another and take longer to get readings due to fluid restrictions, since a large volume of fluid has to transfer between bottles for a small change in fluid height. But the fluid height (not volume) is the only thing equalizing hydrostatic pressure.

Realize that the height of the fluid is linearly correlated to pressure, no matter what the area of the tube is. Since the height of a baby bottle might be 6 inches, and ATF-4 is about 1/13th as dense as mercury, 6 inches of ATF-4 = less than 1/2 inch of mercury or less then 1/4 psi differential.

The only way it's more forgiving is that fluid won't be sucked up. And it's more compact. But it's measurement range is tiny, and it takes a long time to reach equilibrium. With four tubes, you make all corrections without having to shut the engine down and pulling lines off to recheck too.

 

when you made yours did you use glass bottles or plastic?
why didn't you just put water in the bottles?

 

Tinted water would work great, I guess.

 

Glass bottles
Water does have a slightly higher density, but it's still has a density of 1 g/cm3, where mercury is 13.5 g/cm3 and ATF is .85 (I got the 1/13th wrong, that's comparing to water). When it comes to a U-Tube manometer, h = h = h, doesn't matter what area of the tube is, and P1-P2 = density*h*g.

I'd say don't use water, because you don't want to suck water up into the engine.

A 3 ft column of ATF can measure a differential pressure of 2.26 in of mercury, which means a measurement range of 2.26 inches on a mercury based carb tuning tool (where the mercury tool might have 4-6 inches range). That makes the AFT tool much more precise.

A bottle tool is just as precise at equilibrium, but it's measurement range is just 0.37 inches of mercury, which is 0.37 inches on a mercury based tool. Hardly usable.

Unless you understand the 2nd order differential equation governing the height of the fluid in the bottle tool, it's pretty useless at measuring pressure differences without 1. being VERY close to start with, and 2. waiting a LONG time between adjustments for a static equilibrium.

If you filled your bottles with mercury...you might be on to something...

 

So, something light is great in the tube tool but not great in the baby bottles, where it has to be dense but still fluid. Chainsaw oil is dense but maybe too sticky, right?

 

No, the greater the density the greater the range (and lower the precision). Water isn't good because you don't want to suck that up into the engine. ATF-4 is a good alternative although it is less dense than water because it doesn't hurt the engine if ingested. USE ATF-4, regardless of density.

Baby bottles are just bad, due to the ratio of the area:height. Look at the equation I gave for measuring hydrostatic pressure. The AREA of the column doesn't matter at all, by increasing it, you are just increasing the VOLUME of fluid to get the same HEIGHT measurement. HEIGHT is all that matters when measuring differential pressure. A small mercury column would be best for this situation (considering density and measurement range alone).

Chainsaw oil won't be dense enough. Mercury is a metal, with a density 13 times that of water. Most oils (or all maybe?) are LESS dense than water.

There's a reason that mercury has been used for centuries to measure pressure, until is was discovered to be so toxic. No other common liquid is good for measuring pressure due to their densities. The Morgan Carbtune tool doesn't even use Mercury, it uses METAL weights, and the Motion Pro tool uses some proprietary fluid and valving/diaphragms that must be synced before your hook them up.

 

Re: How can i synchronizing xj 750 seca carburetor without c

Unless you understand the 2nd order differential equation governing the height of the fluid in the bottle tool, it's pretty useless at measuring pressure differences without 1. being VERY close to start with, and 2. waiting a LONG time between adjustments for a static equilibrium.

this makes me wonder if you've ever used a bottle setup

 

Bottles would work better if they were slimmer, this is what I understand. And if you could stretch these bottles enough, they would look like...tubes and then would be very efficient, right?

That said, if 1/4 inch inside diameter tubes give accurate measurements, could you explain why do we need a restrictor as small as a WD40 spray tube for each vacuum tube? I don't understand that part.

 

Polock, I have, and it didn't work very well. I still have the bottles packed away in a box. Have YOU tried the 4 tube, 3ft tall ATF tool?

I kept over shooting the adjustment because the fluid height didn't respond fast enough. It might "look" balanced, but how long to you actually sit there watching after each adjustment? The fluid keeps moving. The rate of height change might be imperceptible at a glance, but give it a minute and you'll see that the fluid is still moving. It's an exponential decay, and it's hard to SEE it unless you are actively measuring the height. I suspect most people look at it and just say "good enough."

Heck, some people even argued that the HEIGHT didn't have to be the same for the pressure to be the same, just that the fluid doesn't move. But that doesn't make physical sense at all.

The physics of hydrostatic equilibrium of u-tube manometer is simple. I used them a bunch in college for aero-space applications because they are VERY good at measuring small differences in pressure, like the difference between static and dynamic pressure to determine air velocity. This is a similar application.

But by creating two columns with large restriction between the two, you take longer to reach static equilibrium (or something close enough to it, since the vacuum signal is oscillating). It measures the same thing, just much more slowly.

Manometers have thin columns for a REASON. You don't want the viscosity of the fluid to have a discernible effect on the time it takes to reach static equilibrium (which is an exponential function...of course, because it's a solution to the 2nd order differential equation).

quebecois59: it's not a question of efficiency, energy loss is of no concern. It's a question of time constants to reach equilibrium, and range of the differential pressure that is available to the tool.

The restrictors damp the vacuum signal. The air column between the fluid and restrictor oscillates around some mean value, and you are comparing this mean value in one cylinder across all of the others. When you first turn the engine on, the pressure on intake is much lower than the air column, so air will flow out to equalize the pressure. But when the intake stroke ends, the vacuum signal is gone and the pressure in the air column is lower than on the intake, so fluid moves down, until the next intake stroke. A quasi-static equilibrium is reached when the mean of the oscillations of the air pressure (and their for fluid height) don't change with each cycle. Restrictors reduce the amplitude of the height oscillation of the fluid, making it easier to read. With out them, the measurement is noisy due to the fluid jumping around.

 

"With out them, the measurement is noisy due to the fluid jumping around."

I understand.

I asked the question because my brother has used an homemade balancing tool on his XS650 twin-engine. He didn't put any restrictor in the tube and it didn't seem to bother him at all. Maybe it is more important with our XJ four-in-line engines to get more accurate measurements to have the carbs well balanced.

 

Honestly I've never tried it without the restrictors. When I saw them suggested on this site, and complaints of the measurements being too noisy to read without them, it just made sense to me to use them, so I made them.

I'm also not sure if the effect would be different between a twin and inline four. One the one hand, each column is experiencing the same pulse once per two revolutions. On the other had, fluid is being drawn back by the other cylinders 3 times per 2 revolutions. Feel free to try without restrictors.

 

The goal is to achieve the same Manifold Vacuum across four cylinders.
All you need is a reliable Vacuum Gauge.
One.
Keep the rpm's constant.
Measure the Vacuum of Number-3.
Write it down.
Measure the Vacuum of Number-4.
Adjust 4 to match 3.
Keep the rpm's constant.
Measure 2.
Write it down.
Measure 1.
Adjust 1 to match 2.
Keep the rpm's consant.
Adjust 2 to match 3 & 4.
1 goes along for the ride.

Use a Vacuum Restrictor.
The Gauge pulsates too strongly without it.

http://xjbikes.com/Forums/viewtopic/t=2 ... gauge.html

 

Well, thank you for all these explanations. I'll try without restrictors and comment here then.

 

well yes , the 4 tube board, a 2 tube board and the single vacuum gauge with a 4 gang valve and the bottle setup. that's why i can't understand your statement. the gauge and the bottles don't need the bench sync to be close at all, the engine can run as long as necessary to make adjustments without shutting it off or sucking stuff into the engine then putting more liquid in the hoses. if your overshooting your adjustments, you just need to take your time.
how long do i watch it? long enough, sometimes long enough to tweek the mixture screws.
i've been in engines from .020 to 427 ci and never once did i need to understand the 2nd order differential equation so i'll just forget i read that

 

Rick how precise is your Vacuum gauge? I've always wondered how precise we need given that there is no spec on the difference in vacuum pressure. Using my 4 tube tool, I estimate that I can balance the carbs within 1" of each other, with is equivalent to 0.06" of mercury or 0.03 psi. Likely that's way more precision that is needed.

Polock, just because you never used diff-eq to dive into an engine doesn't mean that someone didn't need to make that engine. Differential Equations and their solutions are great for modelling dynamic processes. It explains why the response is different between the two manometer set-ups. Sure you don't need higher level math to tweak a couple of screws, but it helps to explain exactly what is happening.

Another benefit that I've found to the 4 tube tool is that once you dial in the sync, you can leave it on when colortuning, and re-sync after each cylinder adjustment, to catch the case where a large mixture improvement throws off the previous sync.

 

"Another benefit that I've found to the 4 tube tool is that once you dial in the sync, you can leave it on when colortuning, and re-sync after each cylinder adjustment, to catch the case where a large mixture improvement throws off the previous sync."

I like that one!

 

"A large mixture improvement, ... " ???

What mixture gets vastly improved while you are minutely adjusting the Throttle opening? (my-nute-lee)*

The Manifold Vacuums are adjusted at rpm's close to Idle otherwise the gauge gets pinned or the medium in lines and bottles (whatever) gets sucked into the Plant.

After initial ColorTuning, ... Fine-tuning the Pilot Mixtures involves moving the Pilot Mixture Screws about the width of a Dime or a Nickel.

 

Thanks all you guy .Baby bottles I think its gonna work let's try.

 

But the initial color tuning can throw off your sync. I'm sure any method of syncing works when everything is close, but we're also trying to get to that ball park too.

Measuring at idle is important; however, fluid doesn't just get sucked out of a manometer if the idle increases due to an improved mixture/sync, since all 4 are "fighting" each other for the fluid.

 

Manbot wrote:

But the initial color tuning can throw off your sync. I'm sure any method of syncing works when everything is close, but we're also trying to get to that ball park too. [/quote]

No Leaks, a good bench sync and idle mixture screws set 2.5 ~ 3 turns out will put you in the ball park. Like Rick said the "running" adjustments will be mi-nute.

Gary