After purchase of the Yamaha Tracer in July, I read posts on the Tracer Group in Facebook about a digital peaking manometer from Digi-Sync that I found very interesting.
If you've ever used the mercury-type manometer, like me, you probably find the bouncing around of the mercury in the vacuum tubes while the engine is running calls into question how accurately you're getting the synch squared up. A bigger issue for me and my dated Pro-Synch is my understanding that the mercury in the vacuum tubes of a liquid manometer actually evaporates over time. The idea of a digital meter is quite attractive.
Yes, there are and have been other digital solutions, but when I looked at the Digi-Synch web page, I found their tool to be a reasonable price. The company offers a 2, 4 and 6 channel device with pricing of $129.99, $159.99 and $189.99, respective. That's just not a lot more than my 4-channel Pro-Syn.
Given the reviews that I've read and my belief that the Pro-Synch should be replaced, I went aheard and dropped $159.99 plus $12.50 shipping on a 4 channel Digi-Synch Digital Synching Manometer and was able to put it to work at 630 miles during my first running-in maintenance.
Whether my old Pro-Synch or the Digi-Synch, performing the synch procedure is very simple...once you can get to the throttle bodies. However, getting to the throttle bodies requires considerable disassembly of the body; panels, tank, and air box. And then you have to put it all back together!
As it relates specifically to the Tracer 900, there are some YouTube Videos that show the disassembly and the biggest takeaway is that prior owners have figured out how to avoid removal of the tank by swinging it around and laying it where the seat is located (seat removed, of course). That was helpful, but it's still a lot of work.
The Digi-Synch connected directly to the vacuum tubes and, after warm up, produced a consistent reading across the three throttle bodies at 1212 RPM (spec is 1100-1300, which is at idle on my Tracer). Note that the reading of 26 is the fourth, unused vacuum tube.
The 185 readings for each of the three throttle bodies is in kPa (or kilopascal), which is simply another measure of air pressure (like psi and bar).
Mercury vacuum manometers use a different measure called cmHg or mmHg which is the pressure exerted on the manometer fluid (i.e. mercury) in the vacuum tubes causing it to move up and down. Most mercury vacuum manometers have a range of 0 cmHg to 40 cmHg (or there abouts).
The Tracer Service Manual states that the throttle body readings should not differ by more than 1.33 kPa (air pressure) or 10 mmHg (fluid pressure). My manometer is in cmHg, so the spec is converted to 1cmHG and essentially means that the bars of mercury should not be more that 1cm different between throttle bodies.
A quick online conversion site converted 1.33 kPa to .20 psi. I can't think of what that spec was on past model bikes that I had to do this procedure, but I can tell you that there was no way that my mercury vacuum manometers could be read to that level.
Overall, purchasing the Digi-Synch was a good decision on two levels. First, it's clearly more accurate than the vacuum mercury manometer. Second, it takes only minutes to check and then, if necessary adjust, the throttle bodies; however, by the time the service department at one's local dealer gets the motorcycle ripped apart and then reassembled, the price tag is likely going to run $500. Anyone can do this maintenance.
One last thing!
The rubber vacuum cap on the vacuum tube of the far left throttle body is a little difficult to get your fingers on. This tool will do the job both taking the cap off and putting it back on.
UPDATE August 2021:
I recorded video of my most recent throttle bodies sync check along with the spark plug replacement. Enjoy!
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