jap4lvr from Lincoln, NE brought it to our attention in this post; I felt I could lend my illustration skills and some theory so I'm presenting it here in the How To section.
Do-It-Yourself Synchronization Tool
Parts you will need:
4 identically sized glass or very rigid plastic containers
4 rubber or gum stoppers
10 feet of stiff, clear tubing, 1/4" ID
4 Intake runner adapters
FirstYearDeek wrote:...McMaster Carr and Fastenal (possibly others) sell vented cap-head screws. These 4 or 5 mm machine screws have a 1.5mm hole from end to end. Just screw 'em in and slip the hose over the head. (Hot water and lubricant will help with this)
Tools you will need:
3/8" drill bit and drill
Non-petroleum lubricant (KY or vegetable oil)
Constructing the Apparatus
1. Drill holes in the rubber stoppers. Two of them need two holes, the other two need 3 holes.
RB wrote:...freezing the plugs to make drilling the holes easier and more acurate...
2. Cut the tubing up. You need three lengths of tubing long enough to reach very close to the bottom of two bottles with a generous loop above the stoppers. The remaining length should be cut to four EQUAL lengths.
3. Insert the tubing. Use your lubricant and pliers here. The two-holed stoppers get one long hose and one end of the transfer hoses. The two three-holed stoppers get one long hose each and the other end of the transfer hoses in the two-holed stoppers. The third short hose goes in the remaining hole in the three-holed stoppers. (See diagram... this is much simpler than it sounds)
4. Fill one of the bottles to near the top (not all the way) Then distribute this volume of liquid to the three empty bottles so each has 1/4 of the original volume.
5. Stopper the bottles and arrange as seen in the diagram.
Sagebrush wrote:...I could never get any bubbles to flow through the tubes at the top unless I was very near emptying one of the bottles and beginning to draw air.
6. To get bubbles in the line, suck on one of the long tubes and shake the container. This should introduce fluid and air, making bubbles.
Using the Sync Tool
1. Attach the hoses to the intake runners as labeled above.
2. Start the motor.
3. You should see the bubbles moving in the loops. (Unless you're bike is already perfectly synced!)
4. Start with 1/3, adjust until the bubbles aren't moving between container 1 and 3.
5. Move to 2/4. Adjust until the bubbles aren't moving between container 2 and 4.
6. Move to the side-to-side adjuster. Adjust until the bubbles aren't moving between container 3 and 2.
When all your bubbles are stationary, you're done!
You shouldn't let the level of any one bottle get lower than half of that of the one next to it. If that happens, kill the bike, uncork the bottles and re-distribute the fluid.
You can prevent fluid from being sucked into the motor by ensuring the long tubes don't extend into the bottle. Only insert them into the stopper until they reach the inside surface.
Theory of Operation
Fluid moves between containers due to the varying vacuum levels in the airspace above the fluid. "Nature abhors a vacuum" and an equilibrium is sought by transferring air from one container to the next. There's fluid in the way so you get to see the air move from A to B.
If you had a very poorly synchronized rack and let the motor run for a time, you would eventually transfer all the fluid into one (or two) of the containers, leaving the other three (or two) empty.
Advantages over a manometer
1. Providing your long tubes do not protrude into the bottles too much, it's nearly impossible to suck the fluid into your cylinders.
2. Any fluid can be used, within reason.
3. Pulses are less visible due to the dampening effect of the airspace above the fluid in the containers.
jap4lvr wrote:"...This never needs any calibrating either.
4. ^^ Simply ensure the fluid and air paths are clear of restrictions and each of the four containers will react identically.
TomE wrote:...It does not measure absolute pressure... It does measure differences in pressure, and that's what we want!
1. Tom E is quite right. The absolute vacuum level is less important than the balance between the carbs. (Assuming, of course all the other motor conditions are fine... compression, timing, etc.)
2. Side-to-side (1/3 vs 2/4) balancing isn't quite as accurate as a 4-gauge system; the effect of 1 and 4 on the balance is diminished since it's two air spaces from the transfer tube. BUT as long as the 1/3 balance and the 2/4 balance are good, the 3/2 measure you're making is still meaningful.
Sagebrush wrote:...I couldn't adjust them fast enough to prevent one or two of the bottles from being emptied and another over fill to the point that the liquid, water in this case, was being sucked into the engine.
3. Wide-open tubing will cause very fast vacuum changes and differentials between cylinders may result in transfer of fluid well before you have an opportunity to make an adjustment. Putting a restriction in the long tubes will slow this down. Just be sure to do it the same on all four tubes.
[EDIT] Added advantage from jap4lvr [/EDIT]
[EDIT] Added some information from Sage's post[/EDIT]