DIY carb sync tool

[Hired_Goon]

I made it fairly large as the first time I used it I had no idea how far out my carbs would be, so I wanted the extra length to cover the worst scenario.

So. I have a metre of tube up the pole and just over a metre hanging down to the carbs. Probably about ten metres all up.

I didn't number them but would be a good idea. I just hook them up in the order they come out the top.

I use ATF in there as it's easy to read and the viscosity takes out a bit of the flutter.

I don't have restrictors in there but it would help. I get about a quarter of an inch flutter in the lines but it is easy to match the flutter lines.

The pilot jet idea would be a good restrictor as well so long as none of them were blocked.

Another option is to epoxy some peices of tube from a tin of WD40 inside some joiners in the line. I'm not a fan of screw type restrictors as I beleive if you turn one a little more than others. it could affect the readings.

But the best advice I can give for the first use of one of these is keep your hand near the kill switch.

If your carbs are too far out then the fluid will move fast. Also keep an eye on the bottom to make sure the air doesn't get to the the cross piece at the bottom. If it does it will put air bubbles up the other three lines. Drain and refill is a PITA if you do it to often.

[AlanB]

Hi Goon,

Four-way is brilliant! I have wanted my own synch tool for years to save me crossing town to borrow my buddies one, but could not find mercury, don't trust gauges and could not face swapping a two-way around.

Why did I not think of that!

AlanB

[manshack_one]

I was putting together a parts list for a trip to the hardware store. For each strand I need about 7 feet right? 3 feet up the yard stick and 4 back down? I figure I can hang it right above the tank from the rafters in my garage. That would make 28 ft total right? Plus that 4 way at the bottom.

[randy]

I've been reading about this DIY sync tool for a while now, and I can't help but disagree with the 4-way connection at the bottom.

With the 4-way, if, let's say #1 carb is way out, it will pull the other three way out all at the same time. That would make synching a nightmare.

I think you want to balance the two lefts and the two rights as pairs, then the pairs against each other. BEACAUSE THAT'S HOW THE ADJUSTMENT SCREWS ARE SET UP.

I could see a two-way between carbs 1&2 and also a 2-way between carbs 3&4. That would enable you to balance the pairs of carbs and then the two sets against each other.

Just my .02

[Bud Manley]

I installed some 6" long sections of 3"PVC pipe with needle valves on top. The PVC will hold fluid preventing it from getting sucked into the engine and the needle valves allow adjustment to account for vacuum differences created by hose length, shrinkage and temp differences.
Mine cost about 30 bucks to put together but it was kinda fun putting it together.
\Kinda like THIS one but without the gauges.

(edit)
Oh yeah. Also get high temp vacuum hoses to connect to the vacuum ports on the engine They tend to get hot and melty.

[manshack_one]

Randy maybe Goon will say something about how his has worked. He mentioned using his version for over five years now.

[audijunky]

I have made a 4 way. didn't work too well. All I can say is make sure it is airtight at all the connections. I had problems with this.
Good luck

[Hired_Goon]

Originally posted by randy
I've been reading about this DIY sync tool for a while now, and I can't help but disagree with the 4-way connection at the bottom.

With the 4-way, if, let's say #1 carb is way out, it will pull the other three way out all at the same time. That would make synching a nightmare.

I think you want to balance the two lefts and the two rights as pairs, then the pairs against each other. BEACAUSE THAT'S HOW THE ADJUSTMENT SCREWS ARE SET UP.

I could see a two-way between carbs 1&2 and also a 2-way between carbs 3&4. That would enable you to balance the pairs of carbs and then the two sets against each other.

Just my .02

I understand your hesitation Randy and some of it is valid. But the key to making sure it's not way out is a good bench sync before putting the carbs back on the bike.

Having two seperate tubes won't give you an accurate enough balance between the left and right hand sets of carbs. With this you still set the lefts and rights to be equal and then bring the two sets together via the 3rd screw. But after adjusting the third screw I always find it needs a bit of fine tuning on the others as well.

Using the four way is setting it perfectly. When you adjust the screw between 2 and three the left and right tubes move un unison. Two go up and two go down. If the pipes were seperated it would still work but the movement would be slower as more time would be needed for them to settle out.

I'm not saying this is the be all and end all of syncing tools, but for me it is very accurate and easier to simply match four tubes together than match measured graduations on vacuum guages and carb sticks.

And for anyone who has seen the change in all the tubes after a one degree turn on one screw would know it's impossible to get it perfect using a single vacuum guage.


It's also bloody cheap to do if one doesn't have the money for the commercial tools.


audijunky, did you have airleaks or let the fluid in one tube drop down to the fourway. Air bubbles are a pain and you should drain and refill to remove them. If it is indeed air leaks then you may have to get smaller tubes.

The smaller the internal diameter of the tubes the better it works.

[manshack_one]

Goon, thanks for your response. What inner diameter pvc tube did you use?

[trbig]

You can't have an open reservior as it will suck the oil/water up and into the carbs as it is working with pure vacuum rather than gravity.

Maybe just me... but that makes no sense at all. Carbs don't have that much vacuum. Stick one of those lines in a bottle on the floor and suck on the line and try to draw the fluid up to your mouth... and tell me you aren't fighting gravity. And it's the vacuum that's drawing against gravity?? With an open reservoir, you would be individualizing each carb... they wouldn't depend on what the other carbs were drawing like the closed circuit would. When you buy a carb synch tool, that's the whole point. To figure out what each carb is doing on it's own and adjust it to where they are all working the same.

It's like the YICS system on the XJ. The tube connects all the intakes, so if one isn't up to snuff, it'll draw from the others. It'll show them all drawing the same since they are connected.. like this 4-way system.... even though one or more aren't the same. You are just getting an average. This will probably be close, but I don't seee it being right on. That's why you wouldn't find a commercial unit that connects them all. There are 4 gauges with 4 different lines. It's also why there's a tool for the YICS to individualize each carb.

If you had an open reservoir with all 4 lines dipped into it and you had a thicker hose... say 1/2" or bigger clear line where the fluid went up, it would get too heavy for the engine to draw it up too incredibly far.


Tod

[pggg]

"And for anyone who has seen the change in all the tubes after a one degree turn on one screw would know it's impossible to get it perfect using a single vacuum gauge."


HG, not true, vac gauges are VERY accurate, with a gauge setup as in this pic, it's easy to match all carbs dead on to one gauge, the gauge needle is damped to flicker only a couple of mm's, with a bit of practice it's simple to balance all 4 carbs within a few minutes...

PS either way, gauges or fluids, don't apply ANY downward pressure with the screwdriver when tweaking the carb adjuster screws

[Ken Talbot]

Originally posted by trbig
If you had an open reservoir with all 4 lines dipped into it and you had a thicker hose... say 1/2" or bigger clear line where the fluid went up, it would get too heavy for the engine to draw it up too incredibly far.
Tod

If I remember my high school science classes correctly, and it was a long time ago, the diameter of the hose would have nothing to do with the weight of the column of fluid being supported. With a wide hose, you have more surface area pulling at the column, say at xx pounds per square inch, so you get exactly the same amount of lift with a given vacuum of "so many" inches. What makes a big difference is the density of the fluid. IIRC, a total vacuum will support a column of water of approximately 32ft. Because of its much higher density, that same vacuum will only support a column of mercury around 30 inches.

This is why you can build a vacuum sync tool with 24" tubes into an open reservoir of mercury and not be too overly concerned about the mercury being sucked out, especially if you hang the tool so there is an additional loop of tube above the tool, say another 6 inches or so. Building one with an open reservoir of water, would be a bit cumbersome with the 24 or more feet of tube length you'd want. That's the beauty of these systems that have carbs connected to each end of a tube of fluid, so they're pulling against each other, not against gravity.

[81xsproject]

Maybe I had a junky vac gauge, but I am going to have to disagree. I did a vac synch with my gauge set-up and then connected up my tubing syncher and found there was a substantial amount of adjustment left to be done. Also noted was a significant improvement in the smoothness of the idle from the gauges to the tubing. I have since thrown my gauge in the trash.

[mro]

maybe the operator

I've used a single gauge with a single hose.
Takes awhile as you have to go back and forth, then check it all agin.
Works for me.


mro

[trbig]

the diameter of the hose would have nothing to do with the weight of the column of fluid being supported.

This has EVERYTHING to do with it. The amount of pounds of vacuum is what's pulling an equal amount of pounds of liquid up the column. The WEIGHT of the fluid is what counts.

Just for exageration, let's say that an amount of vacuum will pull say, 16 ounces, of fluid up a 1/2" line to the height of 5 feet. At 8 pounds a gallon for water, it's able to draw one pound of water up the column. Now attach that to a 4 inch pipe. At a height of 5 feet of fluid, there will be what... 2 or 3 gallons of water in there? The same amount of negative pressure that could only hold up one pound, isn't going to hold up 16-24 pounds. It will still only hold up one pound of liquid.
So... if you were using 1/4" line, you will get @ half of the total height achieved if you use 1/2".


P.S. OK.. lol.. Re-reading that.. I am agreeing with the statement. The size of the tube has nothing to do with the amount of pressure exerted on the liquid.. but would have to do with how high the fluid was drawn up the column.