TR2/3/3A SU balance tool

[karls59tr]

I have this tool but have never used it. When the metal ball is screwed in position it does not appear to seal all the way around the edge of the ball? Does this matter for getting an accurate reading or is this part of the design? I thought that maybe the screw shaft was slightly bent? Also what is the smaller screw for?

 

[NutmegCT]

Karl - take a look at the instructions. Also, what "smaller screw" do you mean?

Tom M

 

[karls59tr]

Thanks for sending the instructions. There is a small screw and spring at thre bottom of the glass tube.

 

[JHaydon]

That small screw should be the pivot for the glass tube. The spring is there to hold it tight to the body for a decent seal.

The part that you were adjusting, as you probably saw in the instructions, is the flow control -- and yes, even "fully closed" there should be a gap there for air to come through.

Some carbs / engines draw relatively little vacuum and need that flow control almost closed. I used this tool on a 600cc motorcycle with one carb per cylinder, and even "fully closed" wasn't closed enough to lift the ball. I had to tape over the opening! I think a dual-carb TR should have a much stronger vacuum than that.

 

[bobhustead]

Listening through a piece of fuel hose to the sound of the air at the carb opening is the best way to balance carbs.
Bob

 

[TFB]

I took a hot wire anemometer ,a 1 1/2 pvc pipe with a 1/4" hole in the middle for the probe to get the recommended 4x diameter for laminar flow and best accuracy, with a foam collar to seal around carb face.
THis most accurate method I could think of was no more accurate than listening,as mentioned by bob,with a small hose or watching the pistons go up and down with the air cleaners off.
THe problem with the op's gauge is that as soon as you place it on the carb the rpm changes and engine starts to run rough,
Tom

 

[TFB]

I took a hot wire anemometer ,a 1 1/2 pvc pipe with a 1/4" hole in the middle for the probe to get the recommended 4x diameter for laminar flow and best accuracy, with a foam collar to seal around carb face.
THis most accurate method I could think of was no more accurate than listening,as mentioned by bob,with a small hose or watching the pistons go up and down with the air cleaners off.
THe problem with the op's gauge is that as soon as you place it on the carb the rpm changes and engine starts to run rough.
BTW my Visala Veloci-calc temp,humitidy and airflow meter was I think about $2500 so not an option for most.
Tom

 

[karls59tr]

I took a hot wire anemometer ,a 1 1/2 pvc pipe with a 1/4" hole in the middle for the probe to get the recommended 4x diameter for laminar flow and best accuracy, with a foam collar to seal around carb face.
THis most accurate method I could think of was no more accurate than listening,as mentioned by bob,with a small hose or watching the pistons go up and down with the air cleaners off.
THe problem with the op's gauge is that as soon as you place it on the carb the rpm changes and engine starts to run rough,
Tom

That's good to know. I will probably watch the pistons go up and down with the air cleaners off.

 

[TFB]

Instruments to measure airflow have made great improvements since the uni syn was popular.
An inexpensive,less than $30, hand held vane (pinwheel) anemometer would be my recommendation for somebody wanting to syn carbs by measuring airflow.
Tom

 

[2long]

Hi Tom: Can you give an example of the modern pinwheel type that I can google and check out?

Dan

 

[TFB]

Google hand held anemometer or wind speed gauge.Smaller vanes is probably better to match carb opening,but any of them will be better than a unisyn.
Tom

 

[CJD]

Karl, the gage you have is a good gage. Use the brass knob to control the opening to bring the ball in the tube to mid-range. Then move to the second carb and compare. It works as good, or better, than anything else you can use. If it affects the running of the engine, then it is closed off too far. Once you set the ball mid range, it has a negligible affect on mixture or airflow.

 

[TR Tom]

Still have the UniSyn I bought in ‘74. Is simple and durable (just like the TR) and I’ve never had any reason to replace either one.

I 2nd what CJD says above.

Tom

 

[RGK]

Still have the one I bought for my 12 cyl jag with 4 carbs , most accurate there is, why it is still being sold.