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4-Gauge Synchronization Tool Comparison

1
MERCURY STICKS
Mercury sticks have always been the cheapest method of measuring vacuum synchronization, particularly if you can find a used set of sticks. They also have by far the best resolution and are very easy to use but despite those PROs, mercury sticks have the most CONs to consider. To begin with, mercury is a scary, toxic substance. When you combine that with the fact that mercury sticks can spill and that mercury can be sucked into the engine, turning it into a far more toxic vapour when it exits the exhaust, that should be enough to dissuade anyone from purchasing mercury sticks... but there's more. Because of their size, mercury sticks are not convenient to transport which is likely the most common cause of spills. And, mercury is being outlawed in increasingly more places so even if you were still able to buy used mercury sticks somewhere, getting the refills is becoming more of an impossibility with every day that passes. But, even if you could get all you wanted, there's still one more CON - bubbles. As you rev the engine being tested, the mercury tends to separate into several (sometimes many) small pockets making a reading nearly impossible until you blow into the tool to restore the contiguous nature of the mercury. So, given that there are really only two PROs and so many CONS, mercury sticks should probably be everyone's last choice for vacuum synchronization.
2
DIAL GAUGES
Dial gauge resolution varies quite a bit - some more expensive models have excellent resolution while some cheaper models have poor resolution. A middle-of-road set of dial gauges offers about the same resolution as the Carbtune but not quite as good as mercury sticks or the SyncPro. And although a set of dial gauges is compact and easy to transport & store, they also appear to be the most expensive way to measure vacuum for synchronization. On the surface the cost seems to be the only limitation to buying dial gauges but, having experimentally bought & tested many different gauges, I know that dial gauges have a problem with accuracy and calibration. An impact in the wrong direction can, and likely will, change the alignment of the delicate internal components causing a change in reading. Since most dial gauges don't have an adjustment for static or exponential calibration, any kind of impact tends to end their usefulness. But, even if you were able to find a good set of dial gauges that you could verify reacted to vacuum identically, and even if you were to treat them daintily so as not to effect calibration and accuracy, there's still one more problem. Most dial gauges are spring loaded and built using delicate components, some of which will corrode over time. From the designs I evaluated, it seemed clear that the simple passage of time would cause dial gauges to show different readings. So, although they're compact and have respectable resolution, their accuracy is easily effected by impacts and time which, at the exorbitant price, makes dial gauges unfavourable in comparison to other vacuum synchronization methods.
3
MOTIONPRO SYNCPRO
The MotionPro SyncPro is a unique, enclosed vacuum synchronization tool that's based on a sort of gel substance that isn't toxic like mercury. The tool is compact, has good resolution and is priced better than most dial gauges but not as low as mercury sticks. Right away it's clear that the SyncPro has plenty of PROs but that's not to say there are no CONs. The first and only one I saw calibrated brought up a few questions and concerns. First, unlike dial gauges or mercury sticks, the SyncPro has to be calibrated before each use and that means you need an external vacuum source of some kind. But more of a concern was that the calibration drifted depending on vacuum level. Although the columns were set equal at a particular test vacuum level, when the vacuum level was increased, the columns went out of alignment... pretty dramatically. After some examination it was decided that the unequal response of the four gauge sections was likely the result of production quality issues. For instance, it may have been because each column had a slightly different amount of fluid in the reservoir or perhaps the reservoirs weren't identical in size or maybe the tubing varied ever so slightly from one column to the next. We could only speculate but regardless of the reason(s) for the differences between columns, the end result is the same. If the SyncPro isn't calibrated ***near*** the operating vacuum level of the motorcycle being tested, the reading cannot be relied on to the expected degree. And although the SyncPro is advertised as spill proof, fluid refill kits exist which seems to imply that periodic refilling might still be necessary. So, although the SyncPro is fairly compact, safe and has good resolution and a reasonable price, it's awkward to have to calibrate before each use and there's a real possibility for error. It's an interesting alternative to mercury sticks but not without its own set of problems to consider.
4
MORGAN CARBTUNE
The Morgan Carbtune is another 4-column vacuum synchronization tool which isn't mercury based nor is it fluid/gel based. The Morgan Carbtune has metal rods which are pulled up by vacuum as they glide through precisely machined guides. It has fair resolution; due to its size, not quite as good as mercury sticks or the Motion Pro SyncPro, but more than enough to get good sync easily. The closest comparison in resolution would be that of dial gauges. The price of the Morgan Carbtune is usually higher than a set of mercury gauges (assuming you can get them anymore), par with the MotionPro SyncPro and lower than a set of quality dial gauges so the price can't be called expensive or cheap - but it can certainly be called competitive. The Carbtune and its successors the Carbtune II and Carbtune Pro are by far the most compact choice for a vacuum synchronization tool and that's pretty handy. And unlike the dial gauges which have to be handled delicately, the Carbtune is built a little less fragilely. Minor impacts won't damage the tool and won't effect readings nor do the gauges have to be calibrated before use. Since there is no mercury, no gel or other fluids, there's no fear of death, spillage or any need for refills. Although it looks and sounds maintenance-free, periodic cleaning is necessary to keep the rods from sticking in the guides... which was a significant problem in earlier Carbtune models, particularly as the tools aged. However, the more recent Carbtune Pro has been redesigned to avoid those problems. By all accounts, the Carbtune Pro has been found to be problem-free. It obviously has a lot of PROs and only few or no CONs that have been revealed as yet. It also has one outstanding PRO for which there is no comparison - Customer Service and Product Support. I can say first-hand that no one stands behind their product as confidently as the Morgan folks and no one provides faster, better support. Trust me on this.
 Summary

All things considered, of the four choices mentioned here, my first choice remains the Morgan Carbtune Pro - it's the safest, least fragile, most compact and generally the most user-friendly for a competitive price with customer service & product support second to none.

My second choice would be the Motion Pro SyncPro - despite it's inherent need for repeated calibration, a possible need for occasional refills and a slightly greater difficulty factor in general use, the SyncPro has very good resolution and generates the most stable reading of the four gauges evaluated, also at a competitive price.

The mercury gauges and dial gauges are tied in third place. Although mercury sticks have the best resolution and are easy to use, they're incredibly unsafe, not the least bit portable and damn near impossible to refill because mercury is becoming increasingly scarce and illegal in many places. And although dial gauges are safer, more portable and just as easy to use, they're incredibly sensitive to impacts, impossible to calibrate afterwards and especially pricey for what you get. I wouldn't recommend spending money on either mercury or dial gauges unless you really have to.