Motorcycle Maintenance Test Equipment
The following equipment is listed in approximately the order of usefulness. To do a thorough tuning job you will find a need for each piece of this equipment eventually.
Tire Pressure Gauge
Direct-reading gauges are easier to read. Check your gauge against a master gauge to determine its accuracy. Dirt and hard knocks will change the readings you get.
A compression gauge with dual scales, psi and kg/cm2, is most useful. It's easier for you to get an accurate reading by using the screw-in adapters for the various spark plug threads when kicking the bike through compression.
The test light is faster and handier than a meter for determining if voltage is available, has a sharp probe, and can get into small places. When necessary, you can even poke through insulation on a wire with it. Test lights are available with neon spark plug testing bulbs.
The timing light is used to set the timing of spark plug firing. The neon type is less expensive but gives out less light. The power type needs to be connected to a 110-volt power source or should be equipped with clips for attaching to a 6- or 12-volt battery. It emits a bright light for easy timing.
When a test light won't quite do it, you'll need a voltmeter to determine an accurate output. The ohmmeter will tell you the electrical resistance of a circuit which is just the thing for checking point conditions. Don't leave the meter in an ohm reading position as the batteries will run down. Also, don't try to read the resistance in a power-on circuit as the meter won't last long. Look for a meter that is protected by a fuse or circuit breaker. A combination meter is usually cheaper than two separate meters.
A direct-reading meter, reading is usually in thousandths of an inch, for measuring shaft run-out, rim wobble, top dead center, etc. Screw-in, clamp-on, and magnetic bases are available.
This meter measures resistance with a single scale that reads from 0 to 10 ohms; the first 2 ohms are shown in tenths. Very small resistances can be read in ignition wires, through ignition points, and in other circuits where small differences are critical.
Ammeters are used to measure generator or alternator output, starter drain, or current flow to a specific component. They are connected in series for measurement. A meter scale of 50 amperes will handle most bike applications. Some meters have induction pickups that do not require direct connection into the circuit.
Carburetor Vacuum Balance Gauge
Some bikes have test ports in the carburetors or intake manifolds. When the port plug is removed and a vacuum gauge connected, the gauge readings indicate the carburetor adjustment. Multi-carb engines can be accurately balanced by using a vacuum gauge to adjust each carburetor to the same reading.
A tachometer is used to measure the turning speed of a shaft or wheel in revolutions per minute (rpm) by electrical (ignition), mechanical, or video means. Most motorcycle tachs are the mechanical type powered by a speedometer-type cable driven by the engine. Electronic tachs convert impulses from the primary ignition circuit into engine rpm. Photoelectric tachs react to any bright spot (tape or paint spot) on a tire, wheel, gear, or shaft and give you a scale reading in rpms.
The measurement of sound or noise levels will become necessary as states pass laws governing maximum allowable noise levels for motor vehicles. Initial laws have specific maximums around 86 to 90 dB at 50 feet (15 meters), with the bike at high engine rpm in a lower gear. Most good mechanics agree that maximum power does not come with the most noise. You should too!