Carb Sync Tool

[georgesgiralt]

Is ATF fluid and power steering fluid the same or not ? If yes, it won't work. I've tried it ... The whole length of the tube is covered by oil leaving a hole in the centre and this is a perfect passage for air... or bubbles ... Unusable.
So I'm left with SAE 5W fork oil, coolant fluid with fluorescent green in it (seems to be "thicker" than water) or SAE 20W50 motor oil ....

[Barry]

I think the 20W50 would be too thick and behave the same as the power steering fluid.  The coolant fluid would work provided there is some form of restriction to damp out fluctuations caused by the induction pulses. Fork oil is close in viscosity to ATF so it would work OK in my manometer.  

[montmil]

"Simonizing" the Bings on my Beemers, I've used ATF and "official" BMW 7.5wt fork oil. The fork oil has a nice purple color but it fades quickly in ambient light. (?)

I have line restrictors fitted near the carb vaccum attach points. This really calms and smoothes out the fluid's movement, giving you time to make adjustments before "fogging the neighborhood."

My experience have been that you need to inject whatever fluid you plan on using with your DIY manometer into the lines and let the exotic tuning tool rest for a day or so. Air bubbles will slowly rise and when the last bubble is gone, make time your carb balance project. Impatient types can always finger thump the lines to speed the process.

[georgesgiralt]

So I have finally got the Bel Ray 5W fork oil in one column ! without bubbles... It took me a week and the use of the Mityvac pump to help the air get out. But it works.
The balance does not get back fast. But imbalance is ! That's funny. you turn a screw 1/8 of a turn and one column goes to the roof. If you get that 1/8 turn back the column slowly goes down....
Here are some picture of the contraption : the tubes at the top serve to hold the liquid if a enormous imbalance is applied. The nut at the base of the metal tubes serve to compress an O ring to reduce the flow. The tubes are 110 cm long... Here it is hanging from the ceiling in the garage and it is easy to see when leaning above the carbs...

[georgesgiralt]

Humm ! I do not know why the pictures are leaning horizontally .. Maybe it's too late to work ?
Sorry about that.

I forgot to tell you that the device was initially devised for some sort of adjustment to jet engines. This one was put in the bin because the tube at the top is broken (one side is shorter than the other) ant because one big aluminium nut is missing. It is devised to be filled with mercury, which may explain the presence of the overflow tubes at the top to avoid spilling mercury everywhere ...
I have it in the shop since 20 or 25 years ...

[Barry]

That's funny. you turn a screw 1/8 of a turn and one column goes to the roof. If you get that 1/8 turn back the column slowly goes down....  

That's normal behavior. The fluid seems to cling to the walls of the tube.  1/8 of turn on the throttle stops is a huge adjustment and you should be able to get closer than that before even hooking up the manometer. The balance is so sensitive it should react to smallest adjustment you can make.

[steve hawkins]

I set one of these up for my R65 and it worked really well.

The I put a very out of sync R100 on it and before you knew what was happening the R100 started sucking all the fluid out into the carb and burning it off.  I killed the bike quickly.  

Time to look for a slightly higher viscosity fluid for both the R65 capacity and the R100 capacity.  Not that I have ever let the R100 get that out of tune any more!

Always the last tuning exercise to be done on a hot engine.

Cheers

Rev Light

[Barry]

A simple mechanical syn will get the vacuum balance so close there is no danger of sucking out the fluid.  Feeler gauges will sort the throttle stops for idle sync and then for the cable sync long pointers (wife's best knitting needles) attached to the throttle shafts on both carbs with a short length of rubber hose. They amplify throttle movement so much it's very easy to see if one is opening before the other.

Cost zero.
Risky ? only if she takes up knitting again.