Vacuum gauges work great. Take a look at a previous post of my setup, the adjustable dampeners I cooked up work perfectly also.
https://www.superhawkforum.com/forum...read.php?t=651

These are industrial gauges ($15 ea). They probably are very accurate but it isn't how accurate that matters. What you want to check is if they read the same. To do this just take a 'T' connection and connect both gauges up to a single line and then pull a vacuum on that line. Both gauges should read the same. If they don't read the same it's easy to just mark one of the gauges for the correction factor... eg: write on the face of one gauge "READS ½ LOW". That way you can you'll be sure to be right-on.

The gauges I used in this project are a 2.5" face and read over a 270° sweep. It's easy to read a small fraction of 1" with the thin needle, when the dampening is adjusted the needles are very stable.



adjustable dampening....

 

Nice setup, also fluid filled gauges may prove stable but restricting flow and using rubber hose should be good enough, just check a reference pressure to make sure they read the same, if not just keep in mind the difference while adjusting.

 

Here is a pic of the tool I had for my Ducati. You couldn't use the mercury sticks on it, so this is what they recommended. It just sits on the trumpets. A little time consuming moving it back and forth to get the adjustment right, but works pretty good.

 

I use vacuum gauges but filled with glycerine. They are plenty accurate.

 

I just built the tool from the first posts link. I have a couple questions...

First, I got them synced up and they were clearly off according to the tool... I knew they would be as my "***-dyno" also knew something was up. I set them for balance at idle, but not for higher rpm, was just too much of a pain to do it while giving it gas. My question is, why would you be required to pinch the vacuum line to the petcock to get proper vacuum on this line if when you are running, this line is actually open? I did verify that the vacuum changes a bit when this line is pinched off, but does pinching it really isolate just the carbs? I teed off this line for the carb sync hookup and pinched it between the "T" and the p/****.

Also, I am guessing it would be normal to find a bit of fuel in the 2 vacuum lines I ran and capped off for this after the caps are removed? They were a little damp with gas at the end of the hose...

 

Thought i might bring this thread back, simply because i had a question. I know you guys were talking about making your own carb sync tool, but what about just buying one. I'd like an electronic one, not like the motion pro one's where it's just tubes and mercury. I've only found one, and it's damn expensive:

http://www.kowatools.com/cgi-bin/miv...Code=KEK-55-64

Anybody know of any other companies that make something similar?

-Miles

 

Have you looked at the Twinmax?

http://www.adventuremotogear.com/twinmax-p-28.html

 

I love this forum! Everytime I think of something someone here has already brought it up. You guys are awesome.

 

I know this is an old thread, however I have another question.

I want to make a vacuum gauge synch tool. I new I would need liquid filled gauges, however I wanted to know if a small chamber like a vacuum boost bottle would help to buffer the pulses and make the reading a bit steadier?

 

Not sure how much that would help - 10 in/hg vacuum is 10 in/hg vacuum, regardless of the volume.

If anything would help it would be restricting the orifice size that the vacuum signal is traveling through, just like 99hawk posted, to reduce the amount of flow, thus reducing the size of the pulses. The Motion Pro carb sync tool I have, the SyncPro (white plastic unit with 4 lines and blue fluid) actually comes with little brass reducers to do this job.

 

I have a set like these. Had them for years. Very siumple to calibrate. Just leave on carb as is and hook up the #1 gauge to the other carb and set the gauge while bike is idling. Then hook the #2 gauge up to the same carb and set exactly the same.

Then hook #1 and #2 gauges up to both carbs and perform the sync.

Safe and no mercury around to deal with.

You can also check the sync at higher revs without sucking mercury into the engine. It is hard to see in the pic, but there are little in-line valves to helps with the needle pulsing.

http://www.jpcycles.com/productdetai...&page=&search=

 

do these kits come with everything you need or do I need to go buy an adapter of some sort. If so I'd like to start looking for one before the gauge gets here and monday rolls around before I get a chance to hook it up. I hate having things that I want to use sitting on my desk for a week like that. BTW, new SH owner here. Yes, pics to follow...eventually

 

I also have a set of these guages that I bought years ago. The only other thing that I needed was a carb stick, that I keep per. mounted in the front cyl head, some tubing and a couple (2) inline joints and caps.

Hope this helps.