Carb Sync Guages
03-25-2005, 03:33 PM
#1
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Carb Sync Guages
Here's a set of gauges I use for sync'ing. They're an easy to read 2.5" dial with 1/2"Hg markings on the dial so matching cyls is no problem. I just mounted them both on a scrap piece of wood and made my own dampener to reduce needle fluctuation. The below photo's show some detail of the pulsation dampener but I just took a couple of pieces of scrap metal and arranged them so each vac line can be crimped as needed with a wing-nut for fine adjustment.
These are supposedly accurate gauges but as you know it's not the actual reading that's important. The equal reading is what we want here. To check that both guages read the same I hooked both lines to a 'T' fitting and pulled a vacuum with a brake bleeder. Both guages read EXACTLY the same to a small fraction of 1"Hg (much less than the needle width).
These guages are only about $15 each but very well made. There is even a manual bleed valve built into the top of each guage to equalize the mechanisms for barometric pressure changes.
With a couple of fittings from the hardware store it was ready to go.
I used Wika #38500 30-0" Vacuum Guages
http://www.gaugestore.com/prodinfo.asp?number=38500
Here's the detail of the hose crimp, without some way to restrict the line the guages will pulsate to much to make any accurate use of the readings.
I also made up a tool to easily get to the sync adjustment screw. Rather simple but it is very easy to adjust now, it's simply a 7mm 1/4" socket that's epoxied to some twisted brazing rod (coat hanger will do just as well). It can be bent as needed to easily catch the adjusting screw in 2 seconds with the engine running.
These are supposedly accurate gauges but as you know it's not the actual reading that's important. The equal reading is what we want here. To check that both guages read the same I hooked both lines to a 'T' fitting and pulled a vacuum with a brake bleeder. Both guages read EXACTLY the same to a small fraction of 1"Hg (much less than the needle width).
These guages are only about $15 each but very well made. There is even a manual bleed valve built into the top of each guage to equalize the mechanisms for barometric pressure changes.
With a couple of fittings from the hardware store it was ready to go.
I used Wika #38500 30-0" Vacuum Guages
http://www.gaugestore.com/prodinfo.asp?number=38500
Here's the detail of the hose crimp, without some way to restrict the line the guages will pulsate to much to make any accurate use of the readings.
I also made up a tool to easily get to the sync adjustment screw. Rather simple but it is very easy to adjust now, it's simply a 7mm 1/4" socket that's epoxied to some twisted brazing rod (coat hanger will do just as well). It can be bent as needed to easily catch the adjusting screw in 2 seconds with the engine running.
10-14-2005, 03:14 PM
#4
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Re: Carb Sync Guages
For some reason that makes me really tempted to take a tube and a relatively snug piston and a spring on each side.. Run a hose from each cylender do the tube, and put a spring on either side of the puck.
If the puck goes left, there's more vacuum there, if it goes right, there's more vacuum there.
Does that make sense? Are there any glaring flaws I'm missing?
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Honda cb900c history
If the puck goes left, there's more vacuum there, if it goes right, there's more vacuum there.
Does that make sense? Are there any glaring flaws I'm missing?
________
Honda cb900c history
Last edited by AbeFM; 03-17-2011 at 11:57 AM.
10-14-2005, 04:28 PM
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Re: Carb Sync Guages
I think I picture your idea but I wonder what kind of 'puck action' you'd see since you'd expect some significant pulstaions in your piston. Your idea of attaching both lines to the same point can be done with a 'differential vacuum gauge' which would allow for a very small difference between cyls to be measured and tuned out. I looked for one but the cost of that gauge was much more than two standard gauges ... so....
10-14-2005, 04:37 PM
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Yeah - that's what I was thinking of making - a differential guage. Either with some resiviors (to steal an idea already on this forum) or restrictors. I like the hose-pinchers I saw, too!
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OM352 ENGINE
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OM352 ENGINE
Last edited by AbeFM; 03-17-2011 at 11:58 AM.
10-23-2005, 12:41 PM
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I like the inexpensive set up. Something to add to it would be a small ball valve. To control the needles instead of crimping the tube. This way you could pipe it in to the bottom of the guage itself. Much neater and better control of the flow. The rubber hose may collapse if pinched to hard, resulting in an inaccurate reading. Just a friendly idea to add to your brilliant set up. Small ball valves may be found at HomeDepot.
10-23-2005, 01:07 PM
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Re: Carb Sync Guages
I originally thought I'd end up using some sort of needle valve but wanted to try the hose crimp idea since it was basically free. The current hose crimp works so well that I'm sure I won't be needing to change it. Very fine adjustments on the wingnut allow a very controlable amount of needle dampening, just what you need to easily compare readings down to a small fraction of 1".
The hoses do not colapse at all. Some vacuum hoses you can pick up at your auto parts store are flimsy, the one I used has a somewhat stiffer sidewall. In any case I'm sure there are 50 variations on the same theme that will work fine. Try one out for yourself and change it if needed......
The hoses do not colapse at all. Some vacuum hoses you can pick up at your auto parts store are flimsy, the one I used has a somewhat stiffer sidewall. In any case I'm sure there are 50 variations on the same theme that will work fine. Try one out for yourself and change it if needed......
10-24-2005, 09:38 AM
#9
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My little differential guage went together that same night I posted the idea - two ball point pens, their springs, plastic tips, and some silicon. I used the little thumb-clicker part for the actually slide....
And couldn't find the vacuum port. I think at idle, I'm too rich, becasue pulling the nipple cover on the forward cylender made the bike run a lot stronger. Anyway, I found I need to use the fuel vacuum line on the rear, and haven't gotten around to it. I think my plunger is going to be too lightweight, but will post results, pictures, and such when I do.
-Abe.
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TOYOTA B ENGINE SPECIFICATIONS
And couldn't find the vacuum port. I think at idle, I'm too rich, becasue pulling the nipple cover on the forward cylender made the bike run a lot stronger. Anyway, I found I need to use the fuel vacuum line on the rear, and haven't gotten around to it. I think my plunger is going to be too lightweight, but will post results, pictures, and such when I do.
-Abe.
________
TOYOTA B ENGINE SPECIFICATIONS
Last edited by AbeFM; 03-17-2011 at 11:58 AM.
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