There are three basic types of vibrations:

1. Engine RPM related – If the vibration is related to engine RPM, it will occur in all gears (and possibly even sitting still) at a particular engine RPM or above. This vibration usually can be attributed to the engine itself or anything else that turns at the same speed as the engine, such as the harmonic balancer, flywheel or flexplate, pilot bearing, pressure plate, torque converter, or transmission input shaft. It is also possible for body contact with the engine, transmission, or exhaust to cause an engine RPM related vibration. Worn or broken engine or transmission mounts can contribute to this problem. When driving the vehicle with the vibration present, maintain vehicle speed and try shifting to a lower or higher gear. If the vibration changes or goes away while maintaining the same vehicle speed, then the problem is not related to engine RPM.

2. Vehicle Speed related – If the vibration is related to vehicle speed, it will not be present until you reach a certain speed, and then it will usually start gradually and then become worse as speed increases. In some cases, it will decrease at some point, and then come back again at a higher speed. This type of vibration could be related to your wheels, tires, axles, differential, driveshaft runout, balance, or angles, universal joints, or transmission output shaft. Try the same driving test as above. If the vibration is present in third gear at 50 mph, but shifting to fourth gear at 50 MPH makes the vibration go away, then it is not going to be vehicle speed related and you can usually rule out any rotating component that is further back than the transmission output shaft. At a given MPH, your output shaft, driveshaft, axles, wheels and tires are all turning at a constant speed, no matter what gear the transmission is in.

3. Accel/Decel/Cruise related – A vibration that changes depending on whether you are accelerating, decelerating, or cruising at a steady speed could have quite a few different causes. Generally, this will be related to driveshaft angles or a worn or broken part, instead of something being out of balance. Think about what changes when the engine is under load. The engine and isolator mount loads shift; the load on the pinion bearing changes; your driveshaft angles change, possibly more than they should due to a broken engine or transmission mount; your exhaust, shifter, transmission, etc. could be contacting the body only on accel or decel; if the car has been lowered (or raised), your suspension snubbers could be contacting the body prematurely.

A vehicle works as a system, and you have to understand the relationships between all the different parts when you are trying to diagnose a driveline vibration. Determining if the vibration is related to engine speed, vehicle speed, or engine load will help you narrow down the list of possible culprits, and keep you from wasting your time looking in the wrong places.

Besides the fact that I bought a billet aluminum bullet tach that looks really nice on the bike. Billet tachometers are a great way to customize your bike and actually add a functional piece of equipment to your ride as well. Also some fo your nicer bullet motorcycle gauges have a speedometer as well as a temperature function.

Dakota Digital makes a digital gauge for motor cycles that is both a speedometer and a tachometer. Not just that its also a bullet tach so it will fit nicely on most cruisers and provide a more custom streamline look to your ride. If you are working on a project or a custom chopper Dakota Digital motorcycle gauges are a perfect fit for customizing the bike as well as adding needed functionality. These gauges come in a variety of applications and can be easily installed.

For example the Dakota digital 3015 is a 3 38″ bullet style gauge that is a speedometer and a tach. It has many features and settings like a odometer with resettable trip meter, choose from several settings: speedometer only, speedometer with odometer and trip meter, or speedometer with bar / graph tachometer. A user friendly interface easily allows you to configure these gauges as needed.

Another one of their motorcycle gauges is the 300 series which allows for several display options including voltmeter, oil pressure, water temp or oil temperature as well as fuel level or air pressure readings. Of all the motorcycle gauges available this company has many great multifunctional units available including a speedometer function.

If you prefer a analog tach which is more along the lines of the old school motorcycle gauges. Pro1 makes some really nice analog tachometers. Pro One has several tach’s that are made from billet aluminum which are then chrome plated for a quality finish. One of their gauges also has a built in 4 inch riser. Most of what Pro1 offers is a tach that directly replaces the original handlebar clamp which combines the clamp with a analog tach which makes it easy to install on your bike. Most of the tachometers available thru this manufacturer come with installation instructions and are easily installed.

So really when it comes to choosing a motorcycle speedometer, tachometer or any sort of gauge it becomes a matter of how you want to customize your cruiser. Of course tach’s for sport bikes are also available but those are generally installed in to the dash of the sportbike. Autometer makes a great tach for sport bikes.