Carb sync question

[giff]

Hey everybody, I'm thinking about syncing my lady's carbs. Somewhere I seem to remember someone using only one vacuum gauge that was split into 4 hoses with separate cut off valves. They made a mark on the gauge where #3 read and matched the rest to it. Would that work? Or what about only using one gauge and individually doing each intake and matching them to the #3 reading? Does the vacuum change or something? What do you all have to say? Thanks, giff

[Bobbo]

It can be done that way (use the archive search here to see a lot of discussion).  The main difficulty in using one gauge is that the vacuum reading will change with RPM.  As you make adjustments to the throttle butterfly, the RPM will change with it.  You will need to make a manifold that has valves on all vacuum hoses, and constantly switch between #3 and the one being adjusted.

[Ricky-D]

The most important activity to doing an accurate and satisfying job of synchronizing the six carburetors is maintaining the same rpm with each adjustment change.

Even though this is dealt with in the manual directions regarding synchronizing the carburetors there is little emphasis on the importance of this particular item.  The suggestion is to use a more responsive and accurate rpm indicator than the one that is on the bike. I guess this is the clue!

Whatever,,,, you get the idea!

Failure to do this little bit properly will result in an unsatisfying synchronization of the carburetors.

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[Patrick]

I think I'm about the only one that uses a single gauge.. I run vacuum tube from each intake to a convenient location and plug each line. The gauge is connected with a ' T ' . One line to #3 and the other to any other line that you decide to use.. I use forceps to pinch off the line not being checked.. Just set all to #3.. It is important to keep checking as you make adjustments and the engine speed should be the same as mentioned.. Its easy to set them to a needle width which is about .5 in/hg.. Honda spec is 1.6 in/hg.. It took longer to type this than to do the job.. If your gauge has no provision for dampening then a pair of forceps will work for that.. I dampen to just allow a very slight needle movement.. You do need to work quite fast cuz the cooling  fan turning on will screw things up, a good portable fan can help eliminate this problem..