homemade carb sync

[tlg1100]

I have seen the threads on these homemade carb sync tools made of plastic tubing filled with water or oil.I want to know if they work.Had mercury manometer but broke it years ago.Was trying to order new one but was told back order from now to who knows when.would try any of homemade ones if they work??

[Steve]

Many have tried various methods with several degrees of success.

Might be hard to find a mercury gauge any more, so your best bet might just be the best unit, a Morgan CarbTune.
With the strength of the Dollar against the British Pound, you can now get one for less than $90.

.

[reddirtrider]

Water will work, it's just lighter and you'll need longer hoses. Place a bucket against the garage wall, put 4 tubes in it and run them up the wall to the ceiling. Then hook up your carbs. Depending on the diameter of the tubes, the water will rise to a point then stabilize. Use the entire wall to the ceiling because you want enough room so you don't suck the water into the carbs.

if you want it really trick, put some dye in the water so it's easier to see.

[Steve]

Water will work, it's just lighter and you'll need longer hoses.

Boy, howdy, he's not kidding here.

I just looked up the conversion factor for cmHg to in H2O. Assuming 20 cmHg (a nominal value), you will need to have 107" of water column available. When you rev the engine then cut the throttle, 25 cmHg is quite possible. For that, you will need 134" columns.

In other words, you will need about 11 FEET of water column to match the 10 INCHES of mercury.

.

[reddirtrider]

Boy, howdy, he's not kidding here.

I just looked up the conversion factor for cmHg to in H2O. Assuming 20 cmHg (a nominal value), you will need to have 107" of water column available. When you rev the engine then cut the throttle, 25 cmHg is quite possible. For that, you will need 134" columns.

In other words, you will need about 11 FEET of water column to match the 10 INCHES of mercury.

.

This is true. Now, how you can scale the water column down to a reasonable distance is to use a larger diameter tubing than the one used for the mercury.

Everything depends on the diameter of the tubing.

[spyug]

I don't know how they would work with a 4 cyl engine but I have a "yardstick" that I tune the XS with. It works slick as butter. I think they call it the $1.44 Manometer or something like that on the Internet. The design has been out there for some time. You need about 10 feet of 1/4" (o.d.) clear hose, a yardstick, some tape or zip ties and ATF fluid. ATF is denser than water and won't lift as high under vacuum nor will it cause a problem if sucked into the engine.

Take the hose and find the midpoint. Tape that to the bottom of the yardstick and run the tube up either side of the stick. Tape or zip tie in place. You will have a "U" shape with about 2 feet of lose hose on each side at the top. Fill hose with ATF so that at rest the fluid runs to about 10 inches or so from the bottom. Now some folks put some thinner tubing or partial plugs in the tube mouths to act as restrictors ( i.e. to keep the fluid in the tube and not sucked out. I didn't.

Attach each tube mouth to your vaccum barb on the intake manifolds and fire up. If the synch is way off the fluid will be sucked up one tube and into the engine. Dial down that carb, refill the tube and try again.

The fluid will dance in the tubes with the firing of the engine but when revved will level out. What you want ot achieve is a fairly equal level at idle and an equal rise at revs. Nothing more complex.

I believe you could use 2 of theses for our bikes and I think I read of one using a fish tank valve of some kind to incorporate 4 tubes but I'm not sure how they would work. I was also wondering about the vacuum guage setup and I was going to try and round them up to build a rig.

The Morgan unit does look like the cats azz if you want a compact and accurate rig however.

Let us know what you get.
Cheers,
Spyug

[Veez_strom]

I've used the ATF manometer successfully with my V-strom.
But it is a v-twin. The goal there is to adjust so that the fluid height in either side of the u-shaped tube is equal.

I wondered if/how this could be adapted to a 4-cylinder as well. I ham anticipating a carb rebuild and will need something to balance them.

I'd like to hear more on that. I'll stay tuned.

[rustybronco]

a container of atf, larger diameter tubing, some adaptors from Z1 http://www.z1enterprises.com/detail.aspx?ID=3262
Hummmmm?

water...
13.595 in H2O = 1.0 in Hg
10 in Hg = 135.95 in H2O = 11.329 ft

area of a circle Pi r^2

area of .25 in tubing = .196
area of .375 in tubing = .441
area of .50 in tubing = .785

assuming the tubing used in a Manometer is .25
.441 / .196= 2.25
11.329 / 2.25 = 5.035 ft

.785 / .196 = 4.005
11.329 / 4.005 = 2.82ft

Correct?

[Steve]

Larger diameter tubing, meaning more water weight, will also have more surface area on top to pull up that extra weight. That will exactly offset the extra weight of the water column, meaning that the height will remain the same.

That is the beauty of using a liquid column for vacuum/pressure measurements. Diameter is irrelevant.
You can use a 1/4" tube right next to a 1/2" tube with the same results.

.

[nert]

Instead of paying attention in science class i was thinking about motorcycles!

[rustybronco]

Well pay attention and help me find a "common" high density liquid. (other than mercury or tar like substances)
a.t.f. ain't going to work.

[salty_monk]

Transmission oil. 90w is pretty thick. I might invest in one of the morgan's some day soon.

Dan

[BassCliff]

Well pay attention and help me find a "common" high density liquid. (other than mercury or tar like substances)
a.t.f. ain't going to work.

Two-stroke oil has been mentioned. It won't hurt anything if it gets sucked into the motor.


Thank you for your indulgence,

BassCliff

[salty_monk]

Somewhere on here someone actually got a techie from Motion Pro to admit what the fluid was in their 4 tube setup. The blue fluid. I can't remember what it was but it was definitely something common or two common things mixed together.

Dan

[nert]

Lithium Metatungstate, about 3 times heavier than water. Only cost about $450.00 a liter.