Digi Sync Hook Up

[CaribouHunter]

Can somebody with a Digi Sync help me?  I emailed the guy that I bought it from but he never got back to me, about 3 or 4 weeks ago.  The directions/video do not really show you where to hook up the long tubes from your Digi Sync.  There is a small 2" vacuum line that goes from the top (behind) each carb, and attaches to the bottom of each carb.  Do you pull off the top or the bottom? And, what do you do with the small 2" hose that comes with the kit with the stopper in the end?
Thanks so much. 

[Dak44312]

Don't disconnect anything on the carbs. The vacuum lines on the DS connect to the inside base of the intake tubes. You need to pull the vacuum caps/line off of each one. If you are still using a OE petcock, you'll need to fire up the bike long enough to get vacuum to the petcock and then clamp  that line before you remove it from the intake. It is the rearmost line on the left side. The caps  will likely be a little brittle. Be careful with them. I just ordered one and haven't received it yet, so I'm not sure about the hose with the stopper. It's probably used when you have less than 6 carbs.

[Pappy!]

Am sure BonS will be along to give you an answer.
The extra small tubes he included in the kit you purchased are to replace any of the vacuum tubes you pull off of the bases of your intake runners to hook up the long tubes to. If they are damaged by pulling them off, you have spares.
The information is also available to you if you go to the top right of this page and so a simple search. Tons of information on it.

[nogrey]

I bought one and have used it several times now. Here's what you do:
1: Pull all the hoses or caps (depends on if your bike is de-smogged) off the back of the down draft tubes. These are the six shiny tubes that come from the air box down to the carbs. Each tube has a ~1" vacuum port on the back. It's accessible without dis-assembling anything.
2: Connect all 6 tubes. On the left side (as viewed sitting on the bike) this is #2, #4 & #6 (as viewed from front of engine to back). On the right side (as viewed sitting on bike) this is #1, #3 & #5.
3: Turn on the dig-sync and let it calibrate.
4: Take the vacuum tube that came off #6 (goes to petcock if you have OEM) and suck on it while you start the bike. Once the bike is running you can clamp this hose with hemostats to retain vacuum on the petcock.
5: Let the bike warm a few minutes.
6: Adjust the idle to 900 RPM.
7: Using #3 reading as a reference (follow the tube from #3 up to the digisync) begin adjusting the balance screws until all carb readouts match the reading from #3. Remember to rev the engine briefly after each adjustment to all adjustments to stabilize.
8: After you have balanced all 6 carbs, and they are stable at 900 RPM, slowly bring the RPM up to 3,000 RPM while watching the digisync readings. They should all follow and stay very close to the same. If one or more do not you most likely have a carb issue (hole in diaphragm).

Hope this helps. I know Bon S was at Inzane two weeks ago and was insanely busy. I've seen him respond on this board since we got back.

Feel free to give me a call if I can assist in any way. I've sent you a PM.

[BonS]

Can somebody with a Digi Sync help me?  I emailed the guy that I bought it from but he never got back to me, about 3 or 4 weeks ago.  The directions/video do not really show you where to hook up the long tubes from your Digi Sync.  There is a small 2" vacuum line that goes from the top (behind) each carb, and attaches to the bottom of each carb.  Do you pull off the top or the bottom? And, what do you do with the small 2" hose that comes with the kit with the stopper in the end?
Thanks so much.  

1st - Thank you nogrey for your helpful response. There's little I can add to your description.

2nd - Indeed I did forget to respond to CaribouHunter with the pictures that I promised. So here are a few pics that may help.

This is the intake manifold where you'll be attaching the Digi Sync. You'll temporarily be removing whatever tubes or caps that you have on yours to attach the Digi Sync. After removing each hose you can just let them lay there until you're done. The only permanent hose that you must be concerned with is your petcock hose on cylinder #6 as nogrey pointed out. You can start your engine, pinch the hose off holding its vacuum, and then remove it -or- you can start your engine, remove the hose and work quickly before the engine becomes starved for fuel. If the rpm begins to drop then temporarily hook this hose back up to allow fuel flow once again. After about 10-15 seconds you can pull it back off and resume your synching.


This is a manifold with the vacuum plug attached. Your original vacuum plugs will not look exactly the same but they do the same job of plugging the nipple when you're done.

[gordonv]

Thank you nogrey for your explanation, helps a lot.

#5, shouldn't you warm the bike first, before pulling the vacuum lines.

#6, set RPM using the 2nd version digi sync with RPM display (Thank you BonS for reprogramming the 1st version).

#8, you suggest if RPMs don't match while increasing, that you have a "hole in diaphragm". Diaphragm on what?

Thank you BonS for the pictures, very helpful. I didn't recall that the tubes had those nipples on them on the back side.

Your pic of the installed tubes, shows the hose. It looks like it is connected on both ends. I couldn't blow up the pic to get a better view. Is that correct, and they do connect to something on the top of the engine (pair valves)?.

[BonS]

Thank you nogrey for your explanation, helps a lot.

#5, shouldn't you warm the bike first, before pulling the vacuum lines. When you warm up your engine is up to you. The key thing is to not sync a cold engine as you might not get the same accurate result.

#6, set RPM using the 2nd version digi sync with RPM display (Thank you BonS for reprogramming the 1st version).  

#8, you suggest if RPMs don't match while increasing, that you have a "hole in diaphragm". Diaphragm on what? The diaphragm that operates the slide and jet needle. It's located underneath the chrome dome on the top of the carburetor. If the diaphragm has a tear or hole then the carburetor won't stay in balance as the engine demands more power. I hope to make a video of this happening in the near future.

Thank you BonS for the pictures, very helpful. I didn't recall that the tubes had those nipples on them on the back side.

Your pic of the installed tubes, shows the hose. It looks like it is connected on both ends. I couldn't blow up the pic to get a better view. Is that correct, and they do connect to something on the top of the engine (pair valves)?. OEM setup is two nipples are connected to the pair valves, one is connected to the petcock, and three are simply capped off. As many have customized their engines, by removing or adding equipment, the layout is different. All the hoses can be simply removed while synching. The only critical hose is the OEM vacuum petcock hose. Either a vacuum must be trapped in the hose to keep the petcock flowing fuel or it must be periodically attached to a manifold nipple, or other vacuum source while the engine is being synched.

If you're skilled you can just attach every hose to the Digi Sync except for #6, start your engine, pull off the petcock vacuum line from #6, attach the final Digi Sync hose, and sync before the gas runs out. If things aren't too far off to begin with then this works well.

[gordonv]

I have a Mitty Vac, so will be connecting the #6 line to that, to keep the petcock charged with a vacuum.

Will be doing my fellow rider, when he gets back from his trip to San Diego in July.

[DK]

Bon,

Why not include a "T" in one DS line to keep petcock open while syncing?

This step seems to be causing problems.

Dan

[The emperor has no clothes]

Bon,

Why not include a "T" in one DS line to keep petcock open while syncing?

This step seems to be causing problems.

Dan

After watching Bon do several synch's it seems to me it's not an issue. You have enough gas in the carbs to get the job done.

[John Schmidt]

I have a Mitty Vac, so will be connecting the #6 line to that, to keep the petcock charged with a vacuum.

Will be doing my fellow rider, when he gets back from his trip to San Diego in July.

Be very careful with the MV, you can apply too much vacuum and rupture the diaphragm in the petcock. It takes very little and you'd be better off simply starting the bike and clamping it off before removing it from #6. Certainly a lot less fooling around when done that way. I've actually been able to clamp if off by folding the tube back on itself and simply using a large paper clip.

[nogrey]

I have a Mitty Vac, so will be connecting the #6 line to that, to keep the petcock charged with a vacuum.

Will be doing my fellow rider, when he gets back from his trip to San Diego in July.

Be very careful with the MV, you can apply too much vacuum and rupture the diaphragm in the petcock. It takes very little and you'd be better off simply starting the bike and clamping it off before removing it from #6. Certainly a lot less fooling around when done that way. I've actually been able to clamp if off by folding the tube back on itself and simply using a large paper clip.

My sentiments exactly.

[BonS]

Well gents, I appreciate all your input. Going forward, I've decided that it's simply easier to include an adapter tee with Digi Sync to help out those with a vacuum petcock. The Digi Sync is not only about doing things better but also making them easy to do. Yes, synching can be done without it but I'd rather include everything rather than tell someone to go get a clamp, rubber band, mighty-vac, or need to explain how to work around the issue when I can just give them everything but the screwdriver.

Keep reading below to see that this is not a good plan. I am not including a tee with the Digi Sync as it reduces the accuracy.

[The emperor has no clothes]

Well gents, I appreciate all your input. Going forward, I've decided that it's simply easier to include an adapter tee with Digi Sync to help out those with a vacuum petcock. The Digi Sync is not only about doing things better but also making them easy to do. Yes, synching can be done without it but I'd rather include everything rather than tell someone to go get a clamp, rubber band, mighty-vac, or need to explain how to work around the issue when I can just give them everything but the screwdriver.

Bon, no issues with using the T ? I have a handful of them already, I'll give it a shot.

[BonS]

Bon, no issues with using the T ? I have a handful of them already, I'll give it a shot.

That would be awesome. May I request that you balance with and without it to detect any difference. The count on cyl #6 could change and that would have to be taken into consideration when balancing. Please let us know.

[The emperor has no clothes]

Bon, no issues with using the T ? I have a handful of them already, I'll give it a shot.

That would be awesome. May I request that you balance with and without it to detect any difference. The count on cyl #6 could change and that would have to be taken into consideration when balancing. Please let us know.

You bet. I plan tomorrow 

[CaribouHunter]

Thanks everyone for all of your help and pictures, helps a lot for novice like me.  I have two Valks, and will try to sync my older bike Saturday again.  Should I wait and get a T valve from
BonS or just go ahead and try?  I've posted pics of my Valks on the FB Valkyrie site.  Take care.

[BonS]

I'd guess that nobody's used a tee fitting yet so you might as well proceed. The worst thing that can happen is the engine runs out of gas. And if it doesn't run out of gas you just discovered that your petcock is broken. 

[The emperor has no clothes]

I did the synch today. Did it first with the T on the petcock vacuum line. Only had to adjust #2 and #6. But after that I checked it without the T and I had about 6 points difference on #6 without the T. I believe I had a good seal on everything. So adjusted #6 back to probably close to where it was initially. They are all within 1 or 2 points of #3 (fluctuates between 1 and 2). So if I did everything correctly using the T is not the way to go. Being that mine were pretty close to begin with I never came close to running out of gas but maybe if they were further off you would need to hook up the petcock vacuum line to fill back up. I think someone else should try the T to see if I was correct though. And also I want to say THANK YOU to Bon S for including the vacuum caps in the package. I have visually inspected mine several times and thought they were fine , but once I started to remove the first one it was obvious they were trashed. Only needed 3 because I have 2 used for the cruise control. But those 3 ended up in about 8 pieces by the time I got them off. Took it for a ride around the block and it seems smoother. Thanks again Bon for making these available 

[BonS]

I did the synch today. Did it first with the T on the petcock vacuum line. Only had to adjust #2 and #6. But after that I checked it without the T and I had about 6 points difference on #6 without the T. I believe I had a good seal on everything. So adjusted #6 back to probably close to where it was initially. They are all within 1 or 2 points of #3 (fluctuates between 1 and 2). So if I did everything correctly using the T is not the way to go. Being that mine were pretty close to begin with I never came close to running out of gas but maybe if they were further off you would need to hook up the petcock vacuum line to fill back up. I think someone else should try the T to see if I was correct though. And also I want to say THANK YOU to Bon S for including the vacuum caps in the package. I have visually inspected mine several times and thought they were fine , but once I started to remove the first one it was obvious they were trashed. Only needed 3 because I have 2 used for the cruise control. But those 3 ended up in about 8 pieces by the time I got them off. Took it for a ride around the block and it seems smoother. Thanks again Bon for making these available 

Thank you so much for posting this. I have a Pingle so I had not done this test myself. I do have an OEM petcock in storage so I'll pull it out and repeat your test. I don't doubt your outcome but I'd like to quickly get a second test that verifies your experience. I expect to get this done this evening.

As for the vacuum caps, I'm not surprised. At Inzane I replaced almost every vacuum cap that was pulled off. For some reason rubber hoses last much longer than the caps. It'll be interesting to see how my rubber-hose based vacuum caps fare over the years.

More later. . .

[The emperor has no clothes]

I did the synch today. Did it first with the T on the petcock vacuum line. Only had to adjust #2 and #6. But after that I checked it without the T and I had about 6 points difference on #6 without the T. I believe I had a good seal on everything. So adjusted #6 back to probably close to where it was initially. They are all within 1 or 2 points of #3 (fluctuates between 1 and 2). So if I did everything correctly using the T is not the way to go. Being that mine were pretty close to begin with I never came close to running out of gas but maybe if they were further off you would need to hook up the petcock vacuum line to fill back up. I think someone else should try the T to see if I was correct though. And also I want to say THANK YOU to Bon S for including the vacuum caps in the package. I have visually inspected mine several times and thought they were fine , but once I started to remove the first one it was obvious they were trashed. Only needed 3 because I have 2 used for the cruise control. But those 3 ended up in about 8 pieces by the time I got them off. Took it for a ride around the block and it seems smoother. Thanks again Bon for making these available 

Thank you so much for posting this. I have a Pingle so I had not done this test myself. I do have an OEM petcock in storage so I'll pull it out and repeat your test. I don't doubt your outcome but I'd like to quickly get a second test that verifies your experience. I expect to get this done this evening.

As for the vacuum caps, I'm not surprised. At Inzane I replaced almost every vacuum cap that was pulled off. For some reason rubber hoses last much longer than the caps. It'll be interesting to see how my rubber-hose based vacuum caps fare over the years.

More later. . .

Yes, I would like to see you do it also. I initially thought there wouldn't be any difference between the two tests.

[BonS]

The results are in:

I get a 4 point drop when I add the tee plus a 1-5/8" long piece of tubing.
Without the tee I have to add an additional 14" of hose for a 4 point drop.
Even worse was a tee and 8" of additional hose simulating a petcock hose as it gave 15 points of error!

So, I believe it's the restriction caused by the tee is a real issue. It's acting as a snubber and rounding off the peak vacuum signal. That's not good when you're a peak signal analyzer!!  

Life is a great teacher! I measured my tee and it is only 23% of the cross sectional area of the 5/32" hose. A larger tee would help but I am now very leery of recommending using one at all. It can only lead to errors in the readings.

Funny, as I was writing code and testing performance I became aware of how the sensitivity of the peak readings are to the matching the length of the hoses and that thick-wall hoses give greater peak readings than thin, soft, clear hoses. But when the tee/petcock issue came up I was caught off guard and didn't properly reflect on the lessons learned. So, lesson learned - again.

Nope, no tees! Not recommended. And if you need to extend, shorten or replace the supplied tubing then be sure to do the same for all the tubing so as to keep all the channels matched.

And thank you, meathead, for your help!

[The emperor has no clothes]

That's very interesting. When I was hooking up the hoses I was thinking they would be of different lengths to reach the individual intakes.  It wasn't an issue but I'm glad you mentioned that. Otherwise down the road I might of shortened some  . There is probably a reason why I chop up dead animals for a living instead of engineering tools  . For anybody that hasn't done their synch yet, I'm here to tell you it's very easy and quick. I think there is no need to worry of running out of fuel. Bon with the difference in readings of longer hoses would my hoses reattached to #3 & 4 for my cruise control affect the carb synch's. ?

[BonS]

Bon with the difference in readings of longer hoses would my hoses reattached to #3 & 4 for my cruise control affect the carb synch's. ?

No, the various hoses attached during normal operation won't have any substantial effect on the synchronization. The synchronizing tool is affected because it is sampling through the small brass vacuum port that has an ID of 0.080". This presents a restriction just like the tee does. Every carburetor vacuum port presents the same restriction so the effect balances out for perfect readings.

In normal engine operation this same brass vacuum port has the effect of limiting the imbalances caused by external hoses such as your cruise control and vacuum petcock because the throat of the intake manifold and carburetor is much, much larger than the vacuum port cross sectional area. In fact it's 147 times bigger.

So, it's two very different worlds that are separated by the brass vacuum ports: Inside the intake manifolds and outside the manifolds. Outside the intake manifolds we find that we're very sensitive to having restrictions, different tubing or additional tubing. While inside the manifold we're much less sensitive to it (just don't let it leak!).

[The emperor has no clothes]

Thanks

[larswlvs]

i have a twin max carb syncronizer.Im very interested in the digi Sync but can someone tell me if its that much better then the twin max as far as carb sync goes.

[The emperor has no clothes]

i have a twin max carb syncronizer.Im very interested in the digi Sync but can someone tell me if its that much better then the twin max as far as carb sync goes.

In my opinion it's so much better. You'll be amazed how quick and easy a sync job is with the  DigiSync 

[Lazy]

What difference should be expected from the carbs being sync? performance, mpg, etc????

[The emperor has no clothes]

What difference should be expected from the carbs being sync? performance, mpg, etc????

Mine weren't that far off initially so the difference wasn't huge. But I noticed it was smoother after the sync. I haven't checked my fuel mileage but I would think it would help.

[BonS]

What difference should be expected from the carbs being sync? performance, mpg, etc????

Good sync means that all the cylinders are pulling together like a good team of horses, but one lazy horse and the others have to work harder to try to make up for it so they're down on horsepower.  "Cold" cylinders reduce your horsepower and this puts more stress on the cylinders that are running "hot". Sync matters most when cruising under 70 mph but not much at wide open throttle or above 70. A good sync reduces vibration and gives the engine more horsepower during partial throttle operation which is great for cruising around town and stop-n-go conditions.

[Lazy]

What difference should be expected from the carbs being sync? performance, mpg, etc????

Good sync means that all the cylinders are pulling together like a good team of horses, but one lazy horse and the others have to work harder to try to make up for it so they're down on horsepower.  "Cold" cylinders reduce your horsepower and this puts more stress on the cylinders that are running "hot". Sync matters most when cruising under 70 mph but not much at wide open throttle or above 70. A good sync reduces vibration and gives the engine more horsepower during partial throttle operation which is great for cruising around town and stop-n-go conditions.

I can understand the "team" concept.
Thanks for the replies from Bon s and meathead.