manometer for carb sync

[hoosier jaybird]

I have a 4 gauge carb sync set but have looked at Grandpot's liquid manometer with interest. My question is, since it uses liquid do the tubes need to be pretty much plumb so all levels are truely  equal. And are the length of the sight tubes about 48"? Also are restricters used in line to dampen fluctuations? The set I have has little needle valves to calm down the gauge bounce but like the looks of the liquid system. Any idea what 1" of variation in the tubes relates in inches of vacuum? You experienced wrenchers have been helpful, Thanks.

[Ricky-D]

I think vacuum is normally read as millimeters (MM) of Mercury (HG).

Converting to inches of water (easiest) is somewhere around 25 to 1 with the water being the 25.

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[jimmytee]

If you were to use a manifold of some type and have your individual lines each with their own isolation valve,  only one tube or meter or gage  is needed. This would offset any inaccuracies between different measuring devices because each carb would use the same device for measurement.

[Grandpot]

Hooser:

I use plain plastic tubing, no damping devices.  The board the tubes are mounted on is about 5' high.  I start off with the fluid about 1' above the reservoir.  It's plumb by the eyeball method.  Nothing too precise.  The ATF will bounce around a bit, but you will be able to pick an average point just by looking at it.

The fact that all the tubes originate from a common reservoir assures all the levels are relative to eachother.

I've used this unit for once a year for the past five years.  No drama.

My local independent bike repair shop has borrowed it a couple of times.

This seems to be an item people seem to over think.  It's not rocket science until you open the throttle all the way.  :-)

[hoosier jaybird]

Grandpot, thanks for the reply. I forgot to ask what size tubing you used and where you got your connectors to the pvc reservoir?

[Chillerman]

This is what I use. I don't know if it's the same setup as Grandpot's or not.

[AZdougness]

A clothesline pin clamping a bend in a vacuum hose is a very cost-friendly way of reducing needle bounce. You could also go with a ball/needle valve or pipe x pipe connectors with small orifices. Again, not necessarily cost effective if you have a six gauge set.

Manometer side, using ATF like suggested is a little less prone to bouncing fluctuations due to its weight and if it does get sucked into the manifold won't do much more than fog up the neighborhood.

Like Grandpot said, once you start turning the throttle the necessity for closely synced carbs goes away.

[Grandpot]

Hooser:

Finding the correct size hose might be easier by working back from the carbs.  I don't know exactly where you live or what resourses you have.

Find some black vaccuum hose that will fit on the vaccuum connector on the carb.  The clear hose should be 1/4".  Find a barbed adapter that will connect the black hose to the clear hose.  Most likely you can find this at any auto parts store.  The connectors for the clear hose to the reservoir are 1/4" barb connectors with a 1/8" pipe thread.  Those I found at Lowes (where I bought the PVC).  I drilled and tapped the PVC to accept the 1/8" pipe thread and used RTV to seal the thread.

Make sure you have NO VACCUUM LEAKS and don't over think it.

[97Valk_CT_Euless]

Never worried about the bounce on the manometer, it's real easy to see the "average" since the bounce is pretty quick. I just lined up the averages, wasn't even "iffy". I did like marvel better since its a bit thinner, the tubes change alittle quicker so you see the adjustment sooner. When cool the ATF didn't even return back to level on its own, but using aquarium tees for the manifold is probably hurting me there too, and may be making my bounce less. Nice work on your setup Grandpot. I was a bit less craftsmanlike on mine.

[hoosier jaybird]

Thanks Grandpot and all that chipped in with advice. I think I'll make up a manometer with six tubes. I thought it has to be more difficult than what it appears to be.