Although it's not strictly...
Although it's not strictly necessary, I like to use a few wraps of Teflon tape on the sending unit threads. It prevents the sending unit from seizing in the case and helps prevent leaks. As an alternative, Teflon paste, anti-seize compound or even a dollop of stiff grease work equally well. Don't forget to install a new gasket on the sender; a standard drain plug gasket will work just fine.
The voltmeter monitors the battery voltage, and by extension, the health and load placed on the charging system. Many older/vintage bikes used a charging indicator light to let you know the charging system was functioning properly, if the light came on while you were riding, you could (in theory, at least) reduce as much of the electrical load as possible, and nurse the bike to the nearest safe port. These days charge indicator lights are largely things of the past, so if nothing else adding a voltmeter can warn you of impending electrical doom. For example if the voltmeter normally reads 14.0 volts when you're tooling around at 30 mph, and the needle suddenly drops to 12.0 it's a pretty safe bet that something's amiss in the bikes electrical innards, so end the ride and head for home while you still can.
Just as importantly though, voltmeters allow you to address demands on the electrical system as you ride. For example, at normal cruising speeds, under normal electrical loads, most charging systems put out something around 14.0 volts give or take a few tenths. This provides enough voltage to keep the battery fully charged and perhaps operates a few minor electrical accessories like spotlights or a GPS without problems.
However, as you start adding electrical accessories, such as a heated riding suits and grips (or cocktail blenders) you can overtax the charging system to the point where it can't keep the battery charged. A voltmeter will give you a clear and dead-accurate picture of exactly how much power you're using to run your accessories, so if you've got it all switched on and the voltmeter reads 14.0 volts, or close to it, you're good to go. If the reading drops to 12.0 volts, you might want to turn off the heated grips (at least until the Margaritas are done). Granted, a lot of guys run a lot of electrical accessories without monitoring them with a voltmeter, and do just fine. Unfortunately, just as many overload their charging systems and end up needing a jumpstart after the second coffee break.
Our Motosens gauges (and all...
Our Motosens gauges (and all other electronic gauges) require a switch controlled 12-volt DC power source and a ground. Fortunately, the VTX has an optional fog light connector that provides both in the same plug, so that's what I used. Typically most bikes will have an accessory terminal located somewhere on the bike that provides switched current, and the ground can be picked up anywhere close by. Make absolutely certain that the ignition switch controls the current to the gauge, otherwise power will flow to the gauge when the bike is off, eventually killing the battery.
Because this test bike will...
Because this test bike will soon be returned to stock, I didn't want to make any permanent connections, hence the use of crimp-on terminals. You can hard wire and solder the joint if you prefer or even use a 3M type tap connector, if you must.
Make certain the sensor lead...
Make certain the sensor lead is well protected and routed away from anything, like the exhaust header that's hot enough to melt it. Corrugated plastic sleeve isn't horrible looking, offers a lot of protection, and is easy to use. It's also available anywhere wiring products are sold. Other (more visually appealing) wire wraps are available through a wide range of sources including your local motorcycle shop, or through Whitehorse Gear.
Voltmeters are also a handy way to keep tabs on the battery's overall health. For instance, if you switch on the bike one fine day and see the voltmeter reading down around 9 volts, it's a pretty safe bet the bike won't be going anywhere until you either charge or replace the battery. Again, you can never have too much information.
Although we're using a MOTOSENS oil temperature gauge, and voltmeter, the instructions apply to any clamp-on style gauge. Since mounting the oil temperature gauge entails installing an oil temperature sensor in the oil pan, you might want to combine the job with an oil change. If not, make sure you have enough make up oil on hand to replace any that's lost when installing the sensor.
Motosens Gauges
I'm impressed by these little beauties, they were easy to install, look terrific and are easy to read on the move. They're also dead accurate, which is a huge plus in my book when it comes to gauges. Although we went with the classic, analog needle type gauges, the Motosens lineup also includes "Electronic Line," which uses an LED display (shown here). Both types are available with a choice of housing, mounting and face color options and the Classic line has several different lighting options. There's also a "flat" version (bottom) that can be mounted, via double-sided tape to any flat surface. Lastly, the Motosens line up is available in either a metric (C and bar) or standard (F and PSI) calibration.
Because the gauges are designed for universal installation, the instructions, (which were presumably translated from German) were a little dodgy, but nothing that couldn't be puzzled out in a moment or two. Overall, the Motosens gauges are top shelf and best of all convey the type of information you need to keep your bike running at peak performance.
Resources
Motosens
www.motosens.com
(403) 327-1444
Gauges (ea.) $93.70
Mounting bracket (ea.) $19.90
Oil temperature sensor $26.10