Questionthis 1983 venture is running on two cylinders.I was told it needed a coil.is that the case and how can I check?Please reply to
jodyjackson1@yahoo.com
AnswerHi Joe,
Electrical Testing
(Basic electrical troubleshooting tools)
Few things can be as frustrating as trying to troubleshoot an electrical problem on a modern street or dual sport bike, with their plethora of unidentifiable electrical components, hard-to-remove electrical connectors, sealed wiring harnesses, etc. Much of the trouble associated with fixing electrical problems can be attributed to a lack of proper tools and technique.
Your best friend when troubleshooting bike electrical systems is an electrical multimeter, sometimes referred to as a VOM (Volt-Ohm Meter) or just plain old multimeter. A multimeter reads current (amps), potential (volts), and resistance (ohms), each over a variety of ranges that the electrical troubleshooter must choose. Cheaper model multimeters can be had at Radio Shack for less than $20--more expensive digital models can cost hundreds of dollars. Nonetheless, no garage should be without one.
If you're buying your first multimeter, a cheaper model is recommended for two reasons. First, the measurements you'll need to make when working on your dirt bike are mostly crude kind of checks which require little real accuracy. Secondly, as a electrical neophyte, the possibility always exists to smoke the meter through a wrong connection or test procedure. While superior meters are better protected by fuses, circuit breakers and the like, the ramifications of frying a $20 multimeter are not all that serious. Bottom line: buy the cheapest meter you can find that offers some sort of fuse protection. And buy extra fuses too! An up-to-date electrical schematic of your project is also nice to have, especially when trying to identify various mystery components. However, it is not essential, and in a pinch can often be overcome by a little patience and common sense.
There are essentially three troubleshooting techniques, facilitated by the use of your trusty multimeter. They are: measuring continuity, measuring potential and measuring current. Continuity means that there is a electrical connection between two points, whether they be via a dedicated wire or through the engine or frame. Measuring continuity is especially useful for locating grounds, intended or unintended, checking switch operation, mapping out wiring harnesses (when a schematic is unavailable), checking fuses or connectors for good electrical contact, and so on. Continuity is checked by using the meter to measure resistance, selecting the R X1 scale and connecting the two leads of the multimeter, in parallel, between the two points for which continuity is in question. The R X1 range is used to limit meter pegging (which could potentially damage the meter), and is certainly sufficiently accurate for this simple test.
The meter essentially sends a low voltage signal between the two points (generated by the meter battery) and indicates whether the circuit is completed or open. Open circuits (no continuity) are read as infinite resistance (no meter needle movement), whereas a completed or closed circuit reads as zero (or near zero) resistance (full sweep of the needle). Caution must be taken when using your multimeter in the resistance mode not to run an outside current through the ohmmeter (i.e. checking for continuity between a hot battery terminal and ground), as this will either blow a protective fuse (on meters so equipped) or fry the meter outright. A good precaution is to disconnect the positive battery lead and allow sufficient time for any system capacitors to discharge (on machines so equipped).
Switch your meter to the voltage measuring mode when you need to find hot leads for connecting accessories, check the health of your battery or lighting coil output, and determine if power is reaching a malfunctioning component. A zero voltage check across two points will also tell you it's safe to do a continuity check without fear of meter damage. Voltage measurements are taken with the meter linked in parallel with the suspected potential. Most multimeters have ranges from a couple of volts to a couple of hundred volts, measuring both AC and DC. Surprisingly, you may need both capabilities as the output (lighting) coils of most bikes produce AC. While nearly all street and dual sport bikes rectify this AC voltage to DC (because it's easier on electrical accessories), enduro or trail bikes often run the AC right to the headlight and tail light.
If you're checking an ignition coil output or an unrectified lighting coil output, start by using the AC scale closest to, but not less than 12 volts. For rectified lighting/accessory voltage checks, again choose the scale closest to, but not less than 12 volts, from the DC choices. If the meter reads DC voltage backwards, simply reverse the polarity of the meter leads. With analog meters, it can sometimes be a little tricky determining what the actual voltage reading is, as there are usually several scales printed on the front of the meter. The trick is to look for the higher number of the range you've selected (i.e., look for a 50 if you've chosen the 0-50 VAC range) at the extreme right of the meter and that's the scale that should be used.
Current flow is measured using the ammeter function of your meter. The presence of current flow indicates that your lighting coil or battery is actually accomplishing some work. This is good if a head lamp, turn signal or the like is in operation, but bad if everything is turned off (dead battery syndrome). The ammeter function of your multimeter is useful for locating shorts or determining the draw of a particular accessory. Current measuring requires a slightly different technique, as the meter has to be in line (in series) with the circuit. Most multimeters are capable of measuring a couple of amps draw, way on down to milli- (1/1,000) and even micro- (1/1,000,000) amperes. When using the current measuring function, choose a high current range and work your way down to lower ranges. This prevents the dreaded meter pegging and associated damage.
Troubleshooting techniques are dependent upon the notion that current flow should be zero with the ignition and all accessories turned off. If you're still reading current at this stage, then you've probably got a problem with a shorted or failed accessory. Start disconnecting things until the current draw goes away, and that'll isolate your problem. Beware, however, of charged capacitors discharging and reading as current flow.
Testing Coils
There are two main problem areas with coils: insulation break down and vibration damage. Insulation breaks down overtime and allows high voltage to short to ground. Shellac or varnish was commonly used as an insulators and sealer. On a hot day, the shellac could melt and actually oooze out of the coil. The other problem is vibration. A coil is made up of a primary and a secondary winding. The primary is a few turns of heavy gauge wire, the secondary is made up of many turns of very fine wire – often as fine as a human hair. Through rough handling or extensive vibration these windings can break or short. Today, coils can be rewound with modern wire and an epoxy type sealer that is virtually impervious to heat and deterioration.
Respectfully,
Mark Shively
