Carb synchronization.

[pfg49]

My Workshop Manual says the carbs have a, "vacuum gage union hole". I can't see the hole, but then again I'm old and wear glasses! Where is it please?

 

[Gravelroad]

In front of the place where the choke cable gets in the carb body.

 

[CLEMTOG]

sometimes a brass plug (remove it and fit tube spigot adapter)
sometimes its already a tube spigot (pull off the 3 tubes from the 3 carbs  and tee piece and plumb in vac gauges)

if you have the latter, don't forget to put them back, and while you are there check that there is no perishing (especially on the outer radius of the bends) and that they are a good tight fit on everything that they come into contact with, and are in no danger of chaffing  anywhere or burning on hot fins
CLEM

 

[sfcpiet]

My Workshop Manual says the carbs have a, "vacuum gage union hole". I can't see the hole, but then again I'm old and wear glasses! Where is it please?

What model?

Twins have very obvious spigots in the inlet stub, connected by a length of hose.  Remove the hose and connect the vacuum hoses to the spigots.

Early triples have the vacuum take-offs on the carbs, blanked by small screws along the choke air passage, close to the inlet stub (don't drop them, they tend to collect in the crevice under the starter motor, often unreachable with a magnetic probe.  Stock blanking screws are plated steel.)  You need a spigot to screw into that thread and connect your vacuum hoses.  Later triples already have the spigots installed, connected again with hose and a T-connector. 

500s are similar to early triples.

Before attempting to synch the carbs, make sure valve clearances are as equal as possible, this will ensure maximum gain from synchronised carbs.

piet