Greetings forum members.
Recently Morgan, (our forum administrator) was looking for volunteers to test a new carburetor sync tool. I accepted the offer to test it and post my thoughts on this forum. About a week after accepting the task the tool arrived. I am unclear as to the relationship between Morgan and the tool company, but there was a note in the box that said DigiSync
is a new seller on Amazon and they needed all the help they could get. Their website address is thedigisync.com
I have to apologize to Morgan. I am sure he was expecting a prompt response in testing the tool and my posted report. After I received the tool, life got in the way of bike business for me, and the tool sat for almost a month. There was also trouble with picking a suitable bike to test the tool, more on this later.
In the end I chose my 1972 Norton Commando:
Any manner of testing the vacuum synchronization of multiple carburetors requires a viable access point to connect the tool to a vacuum port between the engine and the carburetor. I have a few bikes that have multiple carbs, but being vintage British, they don’t have any sort of vacuum port as part of their makeup. I found this to be one very frustrating thing in conducting this test. These bikes were built before an accurate sync tool was considered for motorcycle use. My only bikes that have an access point is the Norton and a 1974 Ducati GT750, and its access is a sealing screw threaded into the intake manifolds, which require a threaded stand pipe, something I don’t have, but now have on order. (I will test it after the stand pipes arrive). I thought the tool would be a great candidate to test my 1971 BSA Rocket Three. It has three carburetors, a little more difficult to sync that a twin, and would play to the strengths of the tool itself. Unfortunately, I recently crashed the Rocket in a high side flip that messed it and me up pretty good. It will not be a candidate for testing this tool anytime soon.
The Norton has a balance tube between the carbs which the British did to smooth out the idle and make tuning easier. I don’t think they thought it would one day be used to connect a modern vacuum synchronization tool. After removing the balance tube, there are ready made access points that the tool easily connected to.
The tool itself came in a plastic storage box. This is a nice feature. I am pretty hard on tools as they often scattered and moved around the shop. This plastic case keeps all the pieces along with instructions together. The main tool unit appears to be well made. It is fully digital, there are no fluids or mercury with it so the past problems of evaporation of fluids or the possibility of sucking fluids into your engine are nonexistent. The tool operates on a 9-volt battery
, and has an on/off switch. The tool shipped to me came with a 9-volt battery
that was completely dead. I’m sure it was packed with the switch on. The tool also came setup for four carb testing or less. It has two blanks; I’m guessing the unit can be set up for up to six carbs as required. Also included was four rubber pipes that interconnect between the carbs and the unit.
The unit and the rubber pipes feature quarter turn quick connects. These are good quality and make a very slick setup. Also included were four rubber caps complete with clamps. These are for sealing off an existing vacuum port on a carb intake manifold, but as I said before, our British bikes aren’t set up for this testing in the first place. This kit is obviously geared for more modern multi cylinder bikes that have a single adjustment screw that would adjust the butterfly valves in the throat of the carb or throttle body. Those of you that adjust your twin carb bikes the old school way, e.g. feeling that the throttle slides lift at exactly the same time and that they idle at the same rate by ear and exhaust tone can probably do a fair job. This tool would be invaluable in tuning 3-4 or more carbs. I look forward to testing it on my triple after I fix its unfortunate mishap.
Make sure the bike is warmed up, connect the rubber pipe to each access point in the intake manifold. Turn on the tool unit, and let it calibrate itself. This took approximately 30 seconds. After the unit is done calibrating it settles on an offset value of 25, which is its representation of normal atmospheric pressure.
Start the bike and let it settle to its idle position and observe the tool unit. Each rubber pipe has its own readout. As you can see, my Norton is in very good tune. Both cylinders show the same vacuum value. The value fluctuated slightly, but was never more than one or two points different. The instructions that came with the tool states that any difference in value of less than three points is very acceptable. Any larger differences would require an adjustment of the throttle slide by manipulating the adjustment screws for the throttle slide on the top of the carburetor, or perhaps locating and fixing an air leak around the intake tract. All individual results may vary wildly! It is unclear to me what the value on the readout represents. The goal is to adjust the carb or throttle to be as close to the same as each of the others. The instructions state the unit is capable of accurately measuring pressures and vacuums between 1-12 psi
1.036 to -24.432 inch of mercury (inHg)
68.948 to -827.371 mBar
Summary: I think the DigiSync
tool is a very well made piece of equipment, although our British bikes are not set up for it per se. This was the biggest hassle of producing this post. If you can get past the difficulties of arranging a way to have an access port into the intake stream/vacuum, then this tool is highly recommended. It is very easy to use and I suspect it is highly accurate. My thanks to Morgan for the opportunity to test it and relay my experiences here to the forum. I will test it on the triple, when I get around to the repairs getting it back on the road.