Carburetor syncing

[pete]

Hi all.  It's been a long time since I worked on a bike, but since my daughter surprised us with a 1986 454 I am re-learning and repeating all my mistakes.  The problem I am having is with syncing the carbs.  When I hook up the vacuum guages to each carb the guage needles are wildly and rapidly bouncing around -- which I assume means that there is a vacuum leak somewhere.  This is what we have done so far:
1)  Adjusted valve clearances -- replaced cylinder head gasket, put on a little RTV, and torqued down the bolts as specified
2)  Replaced spark plugs
3) Seafoamed the heck out of the carbs -- drained bowl, filled with seafoam, let sit 24 hours with occasional cranking to get seafoam into the jets, then drained out seafoam, ran several times with carb bowls filled with about 20% seafoam (I have a funnel attached to the fuel line).
4) New air filters
5) Adjusted throttle cables

The bike idles smoothly at circa 1200 RPM and revs up to 8K without problems after syncing; I eyeballed  the dancing guage needles to sort of get an average - revving up to 5K makes them dance around a tighter average.  I can't test drive her yet because I am waiting for circlips to come in the mail to finish the fork oil change.  To try and chase down the vacuum leak, I sprayed every place I could think of with bursts of carb cleaner to localize the leak by the tell tale increase in idle speed.  The only place that gave a positive was the throttle shaft where it goes into the right carburetor.  I don't know whether this observation is relevant as well, but when I move the choke on to maximum, the engine revs up to about 5K, which I would think is opposite to what the "choke" should do.  So, the questions I have are:

1) Am I correct in assuming that bouncing vacuum guages mean that I have a vacuum leak?
2) Is the carb cleaner spray technique adequate to find vacuum leaks?
3)  Can we simply ignore the problem and hope that she rides OK once I have put everything else back together?
4) Is a carburetor re-build in my future?

Thanks so much for your help.

[eaglerider]

Unless someone has messed with the carbs, the sync should be ok. When were the valves adjusted last?

[pete]

We adjusted the valve clearances as the first step in our "tuning" campaign.  Three pair of valves had no clearances when we first opened her up!  Is there anything else that is adjusted with the valves (if there is, we didn't do it)?  We have messed all over the place with the sync adjusting screw, so if it was OK before we started, it now will only be OK if we manage to adjust it right in the context of the wildly gyrating vacuum guages.

[pete]

Update on our syncing woes.  From talking to a motorcycle service tech, it appears that bouncing vacuum readings are normal and due to having short vacuum hose between the carb port and the guage -- the guage is simply reporting the cycling between the openings of the intake and exhaust valves.  The solution is to either use much longer hose or insert a vacuum buffer in the hose.  I did the latter by hooking up a quart bottle in the line (a bottle with a rubber stopper thru which I inserted two tubes, one connected by a hose to the carb port and the other connected to the vacuum guage).  This setup evens out the guage readings which are now steady enough to read.  It also helped to momentarily pinch off the vacuum hose to the guage as sealing it off gives a reading of the vacuum at that instant.