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Why build your own digital carb sync tool?

You need to keep your carburetors synchronized

Is the performance of your old motorcycle or other multi-carburetor engine lagging? Synchronize the carburetors regularly so the cylinders aren’t working against each other.

Are you tired of the mess and fuss of oil-filled plastic tubes? Mercury manometers are great if you have one, but they are fragile, toxic, and no longer available for purchase.

Digital is portable and clean

Digital units are lightweight and portable. Unfortunately, most are made for 2 cylinder engines. If you have 4 carb performance bike or something like a 6 carb Valkyrie or an old Kawasaki Z1300 or Honda CBX1000 things are more difficult and more expensive. Here’s a new and very expensive (~$350) example that only gets you 4 cylinders. There are also the usual fake mercury versions like the CarbTune.

Building your own tools is real

If you have basic shop skills and tools you can build the Digital Carb Sync in a couple of hours. Simple parts and basic soldering are all you need. Loading the software is easy, and the source code is available for people with some beginning code skills who want to make changes.

Digital Carb Sync kits are easy to build

Digital Carb Sync is the original design and kit that makes it easy to build your own digital carb sync tool. Get that bike running at its best. To get started, download the build package—our other items are for convenience. Our Black Label boards are lead-free, can be shipped anywhere, and will save you time.

Digital Carb Sync Built for 4 cylinders

Please note: If you order a product or contact us, please check your spam folder. Depending on your email service, we automatically set our outgoing email to quarantine until you approve.

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Various sources for the sensors


Please note: COVID-19 has made many parts less available. Most suppliers are indicating that new sensors will be available soon. The new good news is I was able to use the OpenAI artificial intelligence engine online to identify substitute parts that were available. This post has been updated to include more potential part numbers. I’ve also added some links for those who can order directly from China.

The sensors are the most expensive part. The price varies between suppliers. They regularly go on sale. There are odd lots available, even on eBay. Sometimes they are much cheaper to buy on a piece of tape roll than on a rail (these are different automated assembly techniques) or vice versa. Some substitutes work just as well. Make 2 or three boards or go together with friends – the more you can buy, the cheaper they get.

Start with a search on ‘MPXV6115VC6U’. This is the standard sensor in the bill of materials. Search on some of the other part numbers, too.

Sometimes these parts are available, but ensure that you are ordering a sensor with a top port – MPXV5050VC6T1,  MPXV4115VC6U,  MPXV6115VC7T.

Shop around. Below are links to a few examples. The board can be set to run on either 5v or 3.3v sensors.

Here’s a search engine that can sometimes find things:

Another search engine that can be very useful is

Another search engine:

Another search engine:

If you can order directly from China, here are a couple of links to get you started. These usually have the lowest price:


Shenzhen Xinzhongtai Electronic Technology Co., Ltd.

Contact us if you find something new, and we’ll check it out. Here are the basics.

You need a vacuum sensor for each cylinder. It should measure vacuum from approximately negative 7 to 10 pounds per square inch up to zero vacuum. Or, if measured in kPa,  negative 60 to 115 kPa up to at least zero vacuum. The part shown in the picture measures -115 kPa to 0. Most bikes will idle and rev in the 7 to 10 lbs per square inch range of vacuum.

It should be in a standard SOM package, with a port, either smooth or barbed. See the picture with a smooth port and 8 ‘legs’.

It should run on either 5 volts or 3.3 volts. These are standard. The board can be built for either. Sometimes a range around the voltage value is advertised in the sensor specs. For example, a spec might say input voltage 2.2 to 4.6 volts instead of just saying 3.3v.

It should output analog voltage, zero through up to approximately 5 volts.

If you find something, compare the spec sheet to the spec sheets of the options below, especially the Digikey. Use the standard sensor from Digikey unless you find something at a great price. 3.3v build option 3.3v build option

Last updated 12/31/2022

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Comments Post

I’ve got the schematic so I’m going to start working on the PCB, buy components and put everything together. Sometime soon I should be able to send you feedback on building the project. I thank You once again for providing the materials to me and the community, and I will keep You updated. Greetings from Germany! Darek.

Thanks for the effort you put into developing the Digital Carb Sync and providing it as a DIY project. I was able to fumble my way through the xloading process and it worked perfectly. You might put a plugin for Digi-Key for fast and accurate product ordering and shipping. Bruce S., Louisiana.

My friend the fancy box builder takes a run at a case! Salem, OR.

David sent this in.

I’m in Christchurch, United Kingdom (not Alabama!) 🙂

I have finally got my laser cut box design to a point where it might be useful to others.

Rick did a nice job on his 6-cylinder build. He also used his 3-D printer with our plans to make a case. Then he added a quick release manifold. Well done!

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3-D Printed Cases

We have design files for 3-D printed cases for the Digital Carb Sync. They are easy to upload to a 3-D printer or printing service. Prices are dropping and you can find many reasonable options. A case is not needed but it looks nice and adds some protection to your device.

The designs are available for download in our catalog.

We sometimes have some samples available for sale for an easy way to add an optional case to your Digital Carb Sync device. Contact us using the form on the About page.

Below is a list of 3-D printing services we have used. There are many available around the globe. The materials available, and the cost, varies. Some offer color choices as part of the printing process. You can dye or paint the cases to your preference as needed. The red case in the photo is from Shapeways.

3-D printed in red
3-D printed in red
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Compatible Arduino Uno R3

Arduino Uno R3
Arduino Uno R3

Using the name brand product is the easiest.

You can find many less expensive substitutes. We see some as cheap as $5 on eBay. We have used them successfully when directly loading the HEX files.

Before buying a cheap board try to find out whether you will need a special driver on your PC. Make sure you get that driver or can get it if you need it.

If loading the HEX file on a cheap board gives you trouble as an alternative you can request, compile, and load the source software using the free Arduino IDE available free at Use the downloadable version. Just copy the library folders included with the build package into the library folder of the IDE. Installing the IDE usually installs everything else you need including drivers for most boards.

See a range of options with this search on ‘compatible arduino uno r3‘.

SainSmart Uno R3
SainSmart Uno R3

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Manufacturing the boards

Black Label Board
Black Label Board

You can buy a board from us or make several of your own.

It is pretty cheap and easy to have boards made. Most places will accept online the gerber zip file included in the download package. Often you end up buying a multiple batch of some size but it is still inexpensive. The service we use sends 10 minimum. We buy the lead-free boards (often required in EU and other countries). Lead-free costs a bit more. You can order from any of the many board shops on the globe. You also can find many local board shops for less where you live.

We use

We buy the black lead-free board using the default options for the rest.

So, make your own, or buy one from us. Your choice will depend on shipping costs and whether you want more than one board.

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Uploading the Bill of Materials (BOM) to Digikey

It is easy to upload the BOM. It will be cheaper to buy the Uno elsewhere, and maybe the sensors. But this technique makes an easy one-stop shopping for all the parts. Follow these steps:

Create an account on

Go to BOM manager and select upload an order.

Upload the BOM file. It’s an XLS spreadsheet file.

Select that info starts on row 2 during file interpretation.

Use the drop downs to match names of the first several columns. The Digikey part number is the first. Quantity 3 is the last one that needs to be matched.

Process the file. Make a cart.

Review the cart. Delete the items you are sourcing elsewhere (e.g. the Uno, the sensors).

You might find solder paste cheaper in your local electronics supply store, but for convenience, you can add this to your Digi-Key order: Solder paste at Digi-key

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Useful information about the hexloader

The Complete Build It Yourself Package includes hex loaders for Windows and Macs. This is a tiny program that will upload the supplied hex software files onto your Arduino board so you can run the program.

An Arduino usually has a bootloader on it. A bootloader stays on the board to manage software uploads. When using one of the hex loaders, you may or may not be loading or even overwriting the bootloader. That’s fine; it just takes up space unless you are trying to load something from the IDE. Then the board needs to have a bootloader. Fortunately, the IDE has an option to first load the bootloader.

Sometimes DigitalCarbSync hex programs are supplied with and without a bootloader. Either will usually work. Sometimes the supplied hex program is too big to load directly if it also includes the bootloader. Just use the other version.

Here is some useful information about the bootloader.