Multi-carb Syncronizer.

[Robert Kenney]

I read michaels post to rhodes and decided to post some advances for flow meters used to help synchronize synchronous multiple carb setups......

Two ways to verify carburetor balance on one of these.
1) manifold suction using a multi gauge manometer similar to the one pictured which is the best way but most expensive.

2) air flow using a flow meter like unisyn .

Or a new meter I discovered and bought, a schleyer carb air flow meter. Found at jcwhitney at the best price

The old unisyn type of flow meter (I have two here now) has a major draw back, it creates a large air flow reduction thus slowing the engine making it hard to get a good consistent indication of flow.

The new schleyer meter does not have that unwanted effect and I would recommend it over any other type of sync tool

use these to synchronize crap like this.

 

[Michael Mayben]

In the old days when we could actually easily access the air horns on single venturi carbs used in multiple arrays, the uni-syn was the goto tool. Worked just fine on solex, zenith, etc. Carbs on limey cars and bing, dellorto, amal, keihin, mikuni twin/multi-carb motorcycles.

Once the induction systems of the japanese scooters became far more sophisticated, then the uni-syn wouldn't cut it and there was no way to actually install without removing the airbox which sometimes meant removing the engine from the frame!

The mercury tube manometer (the original "carb stick" then became the weapon of choice due to it's inherent damping quality. This is a modern version though pricey and the things no longer use mercury (for the most part, some still do):

motion pro - syncpro carb tuner

We usually avoided using the multiple analog vacuum gauge sets as you had to continuously adjust the damping valves in order to get the best true reading, that was time consuming and resulted in inaccurate actual vacuum readings.

Setting up multiple carbs on multi-cylinder outboards was a real bitch since the throttle position is actually set by advancing/retarding the ignition system through the throttle control cable system. That set of multi-vacuum gauges Robert posted was originally developed by the mercotronic subsidiary of mercury marine back in the day. Those are the folks that did the special tools and test instrumentation for mercury dealer mechanics. Clones of those are available today in varying quality and pricepoints:

carb sync | all kinds of automotive tools

 

[Greg R]

Interesting on how this stuff turns up. I was "organizing" the shop,(actually looking for something I couldn't remember where I put), and came across my old uni-syn.

Good post guys.

 

[Robert Kenney]

in the old days when we could actually easily access the air horns on single venturi carbs used in multiple arrays, the uni-syn was the goto tool. Worked just fine on solex, zenith, etc. Carbs on limey cars and bing, dellorto, amal, keihin, mikuni twin/multi-carb motorcycles.

Once the induction systems of the japanese scooters became far more sophisticated, then the uni-syn wouldn't cut it and there was no way to actually install without removing the airbox which sometimes meant removing the engine from the frame!

The mercury tube manometer (the original "carb stick" then became the weapon of choice due to it's inherent damping quality. This is a modern version though pricey and the things no longer use mercury (for the most part, some still do):

motion pro - syncpro carb tuner

We usually avoided using the multiple analog vacuum gauge sets as you had to continuously adjust the damping valves in order to get the best true reading, that was time consuming and resulted in inaccurate actual vacuum readings.

Setting up multiple carbs on multi-cylinder outboards was a real bitch since the throttle position is actually set by advancing/retarding the ignition system through the throttle control cable system. That set of multi-vacuum gauges Robert posted was originally developed by the mercotronic subsidiary of mercury marine back in the day. Those are the folks that did the special tools and test instrumentation for mercury dealer mechanics. Clones of those are available today in varying quality and pricepoints:

carb sync | all kinds of automotive tools

I have used them all, the motion pro mercury manometers, dial gauges unisyn and even home made dyed water vertical gauges and I'll tell you that with big cams the unisyn meters are a bitch. They work well on basically stock engines that have a nice strong vacuum mainly because the low vacuum from a large cam makes the idle circuit very sensitive and the added pressure drop from the u-s meter is almost intolerable. The schleyer gauge only reads air flow thus has little added resistance to flow. Just a better gauge if one was going to buy one.