About the Yamaha DT 6 Volt Headlight Voltage Regulator: Many Yamaha DT’s generate excess headlight Voltage. This is a design problem, as much a stator (alternator) problem as a light bulb problem. Light bulbs burn out eventually. The stator is a copper winding around a laminated core, similar to an automotive alternator or electric motor winding. The big difference is the permanently magnetized rotor, which does regulate the AC Voltage generated. As the engine revs higher, more AC Voltage is generated, at increasing frequency. At high RPM, the combination of excess Volts and vibration tends to blow headlights. Any loose or intermittent AC wiring or switches will generate eneormous Voltage spikes that will blow bulbs.
BUILD FACT: Yamaha built the DT with no headlight Voltage regulator. The headlight absorbs stator Voltage, so to keep things simple the stator makes just enough power. At high RPM the headlight is sometimes not quite enough load. Result: the bulb blows. The headlight circuit is balanced to yield a modest light at idle and low RPM, while giving full brilliance without blowing out at high RPM.
UPDATED LATE MARCH 2018: People considering our parts possibly worthy of their bikes often write us. Today we had a great letter from a reader of the excellent Yamaha Enduro forum. The question insspired updating this page. Our DT headlight Voltage regulator protects both Low and Hi beam headlight filaments, the Hi beam indicator lamp, and the meter lights. All these bulbs are wired together in common, and are thus protected by the regulator.
METER CICRUIT: Our design is aimed at replacing a Yamaha-issued add-on headlight Voltage regulator for dealer installation. The spirit and intent of our regulator is connecting to your bike, just as Yamaha connected their regulator. The retrofit regulator T’s into the Light Blue wire feeding AC Voltage from the Day/Night switch to the meter light circuit. In this manner, with the Day/Night switch in the Day position (headlight Off) the regulator is also disconnected. Because of the integration of the Day/Night switch and Hi/Lo beam switch, the Light Blue meter lamp wire may be the only correct place to tap into the headlamp power circuit between the D.N. switch and the Hi/Lo switch.
HOW IT CAME ABOUT: After years of working on circuit designs, we concluded with a special Voltage regulator to control the excess AC headlight Volts at high RPM. Its simple on the ouside and easy to install. Its durable, able to withstand the punishing heat, vibration and physical shock of surviving on a dual purpose bike. It helps prevent headlight bulb failures caused by over Voltage conditions. We live and ride in a state that will ticket you immediately for a blown headlight, which gave us some motivation to design this part. 6 Volt Headlights are not common and cost more to replace, even if you run a replampable headlight assembly it still costs to put in a new bulb, and night rides are out of the question. Our first bikes were dual purpose machines, we still ride them, and as a result we understand them.
TOUGH: Our DT headlight Voltage regulator is rugged, waterproof, and vibration proof to endure the unique Dual Purpose motorcycling environment. The device easily taps in to the stock Yamaha wiring inside the headlight bucket, specifically the Light Blue meter lamp circuit and ground. Installation is simple, just two wires to connect and you are ready to ride. Excess Voltage is converted to heat inside the regulator. The regulator does not steal power from the lighting circuit while the engine is running slowly. At medium RPM where headlight Voltage is not too high, the circuit monitors the Voltage and stands by, ready to respond. This is super-important, because these old 6 Volt bikes do not generate enough electricity at low RPM to maintain headlight brightness. Any regulator that absorbs Volts at low speed is unsatisfactory – it dims the headlight. Once engine speed picks up enough to generate too much headlight Voltage, our regulator quickly and smoothly kicks in just above 6.5 Volts AC, absorbing only the excess Volts. The headlight receives full design power, while the regulator automatically adjusts to absorb just the extra Volts.
DURABILITY: This device gives you a bright headlight that lasts like it should. Eventually the headlight will burn out, as all bulbs do. The heavy-duty regulator core is rated for 25 Amps of surge current, and 6 Amps of continuous load, more than the total power the headlight stator generates. The automated circuit monitors stator Voltage faster than its generated, so you never notice it working. It throttles along with you, working as needed.
ENDURES: The regulator circuitry is uniquely constructed. Motorcycles are tough on parts. We have seen so many failed bits and pieces over the years, especially circuit boards. Off road and DP riding is especially tough, as are single cylinder 2-stroke engines which usually vibrate harshly at certain speeds. Vibration, humidity, heat, cold, freezing, broiling, roasting, shaking, pounding, jumping, landing, dirt, grit, water, dunking, gas, oil, grease, detergents, pressure washers, and probably more… tend to destroy electronics.
BUILT BY HAND: We built the regulator to endure all that. Each one is hand assembled, tested with a headlight circuit and verified to kick in quickly and work hard. Its not a big Zener diode, either. Its a dozen heavy duty parts working in harmony, built on a piece of military grade FR-4 fiberglass circuit stock. As technicians we have repaired and diagnosed many defective motorcycle circuit boards, so we set out to build something tougher, more battle-hardened. Cheaply built electronics we encounter today, are not up to the standard Yamaha set when these bikes were built. We hand assemble each regulator so the device operates without solder. This involves crimping, wrapping, forming, and several other sturdy techniques that take a lot of time. After passing a functional load test, each unit is then fully soldered, then load tested again. The exterior is American-made high temperature electrical PVC conduit, custom machined inside and out. The regulator functions well in harsh conditions. It survives hammer blows, immersion and heavy vibration, and still perform.
SOLID: Encapsulation in solid thermal compound is not done to hide our work, its done to stabilize and protect circuits from abuse and add waterproofing. A third and final load test assures you get the best quality part we can make. We don’t ship D.O.A. parts because we test everything more than once. When we goof a build, it is caught before it leaves here, labeled Doh! and up it goes onto the wall of shame.
We make stuff that survives on our bikes, to survive all the places you ride. We are proud to offer our gear to you.
Built Strong to Last Long.
If Its This Good, Its From the Labs and Workshops of the Pardue Brothers