Technical: Headlamp
Scott Lange, Dave Hennessey

Guide 7" Headlamps of Interest
Part # High / Low
Manufacturer Reflector Lens Marking Reference
67717-48 30 / 30 H-D (Guide) Steel Cycle Beam 1954/1957 Riders Handbook
- 50 / 40 Guide Steel Sealed Beam Automobile
67717-48A 50 / 40 H-D (Guide) Unknown Unknown 1959 XL Parts, 1959 Service
67717-48B 45 / 35 H-D (Guide) Glass T-3 Motorcycle 1969 XL Service Manual
  50 / 40 Guide Glass T-3 Automobile

1952 – 1958   7-inch Headlamp

The 1952–1956 K-models and 1957–1958 Sportsters used the 67717-48 headlamp, a 7-inch, 6-volt, 30 watt / 30 watt unit. This headlamp was also used on 1949–1958 Hydra-Glide big twins.

This was an early attempt at a “Sealed Beam” unit. The reflector is steel, not glass. It is painted black on the outside, and aluminized or “silvered” on the inside. The light bulb is soldered into the reflector. Then the reflector is rolled over the edge of the lens. Thus it is a sealed unit, and has to be replaced in its entirety.

During the very late 1940s and through the 1950s, the automotive (and motorcycle) industry was changing from 6 volts to 12 volts. These steel reflector bulbs may have been an attempt to inexpensively manufacture lamps of different specifications during the changeover period. Different bulbs and lenses could be installed in the steel reflectors without tooling up all-glass units that would have a limited sales life.

The rear of the reflector has three metal “locating tabs”, and a single metal locating pin. The locating items fit into the locating slots on the headlamp body, and the unit fits snugly to the face of the body. Later manufacture cycle and automotive lamps (e.g. 67717-48B, and automotive trade number 6006) do not fit snugly.

This headlamp is marked “Cycle Beam”, and has an asymmetrical pattern on the lens. Harley-Davidson called them “Seal Ray”. Working (and non-working) units are quite rare today.

Here is a headlamp with a broken lens. The bulb appears to be removable, but is not. What appears to be a bulb and socket is actually just a bulb, soldered to the reflector.

The restorer may need a more obtainable alternative. One alternative is a period automotive lamp, which is similarly constructed with a steel reflector, but with some differences. The lens on period automotive units says “Sealed Beam” rather than “Cycle Beam”, and the lens design is symmetrical. The locating pin on the rear is absent. Like the correct “Cycle Beam” unit, this lamp fits snugly to the front of the K/XL headlamp body.

These automotive lamps have a higher output rating than the Cycle Beam. They are 50 watt/40 watt, the same as standard automobile 6006 would be a few years later. Harley warned not to use automotive bulbs, as they would tax the output of the motorcycle's charging system.

These automotive lamps come up on eBay occasionally, and are described as fitting various 1940s and 1950s vehicles. They are often described as fitting early Corvettes. It is not known if this is true, but that does tend to drive the price up. Of course, you need to find a seller that will guaranteee that the lamp works on both beams, or you may be buying a high-priced boat anchor. (See “Testing Headlamps”, below).

1959 - 1964    7-inch 6-volt Headlamp

Sportsters changed to 5-3/4" headlamps in 1959. But the big twin Hydra-Glides continued to use the 7" 6-volt lamps through 1964. The 1959 Hydra-Glide used the same headlamp shell as 1949-1958. In 1960, the Hydra-Glide changed to a two-piece nacelle with a headlamp “bucket”in the middle.

1959 - One Year Only

Something strange happened in 1959. The 67717-48A headlamp appeared, replacing the 67717-48. It was rated at 50/40 watts, the same as Harley had previously warned us not to use! This is pure speculation, but we think Guide may have stopped producing the steel-reflector Cycle-Beam. The new glass T-3 Motorcycle bulbs may not have been in production yet. If they were, they would not fit the 1959 headlight bucket correctly due to the “landing pads” So Harley used an oddball lamp for this one year. Just what was it? We don't know. Even Bruce Palmer is fuzzy on the 67717-48A.

Could it have been the automobile version of the steel-reflector lamp with the “Sealed Beam”-marked lens. Could it have been an automotive version of the T-3? Could it have been something entirely different? We may never know, as these one-year only lamps may have all burned-out and been tossed away in the last 58 years.

Glass Reflector with Landing Pads

The distinguishing features of post-1959 headlamps are the sealed all-glass construction, with landing pads molded into the glass. The “landing pads” were small pads on either side of each locating tab. The locating tabs, previously metal, were now part of the glass “envelope”. The landing pads cause the lamp to stand away from the K/XL headlamp body, so the retaining ring does not fully hold the lamp to the shell. The result is that while the headlamp can be assembled this way, a good jarring may cause the headlight to shift slightly, then one of the pads “falls in” to the body, and the lamp becomes cockeyed.

This is a problem for fitting post-1959 lamps onto K/XL or 1949-1959 Hydra-Glide headlight shells. Modifications have to performed on the shells to accommodate lamps with the landing pads.

1960 – 1964 T-3 Motorcycle lamps

The 67717-48B appeared in 1960. This is a Guide all-glass headlamp with an embossed “T-3” in the center of the lens. Below the T-3 is the word “Motorcycle”. The motorcycle designation indicates that the lamp is 45/35 watts. These have the landing pads, so they do not fit correctly on the K/XL bodies. The T-3 lamps have three bumps on the lens that can be used with Guide's Safety Aimer headlight aiming system. These bulbs have an ink-stamped 6V on the rear.

Note: The 1965 to 1969 big twin, and 1964 Servi-Car had 12 volt systems. The 67717-64 bulb looked the same as the 67717-48B, except they had an ink-stamped 12 V on the rear. We do not have a photo of these.

T-3 Automobile Lamps

Guide T-3 lamps that do not have the “motorcycle” designation on the lens are automobile industry-standard 6006 headlamps. The T-3s were produced by Guide, but many manufacturers produced 6006s. These are 50/40 watt units, so they are a little strong for motorcycle use. However, many K/XL enthusiasts use them when the correct lamps are not available. Automotive 12 volt units were similar, except marked 12v near the top of the bulb..

Testing Headlamps

Headlamps should be tested with a (6-volt) battery, never a battery charger. Most battery chargers, expecially your trusty 20-year-old job, have a dirty output - they produce DC with a sizeable AC component instead of straight DC. This is because they use a cheap, but reliable, rectifier circuit. Batteries don't care. Modern headlights probably don't care either. But that 50 or 60 year old headlight's filament is probably a little weak from age, so the AC might burn it out. Don't take chances - use a battery!

Trivia - Guide T-3 Safety-Aimer

The T-3 designation actually refers to internal focusing design. These bulbs focus 3 degrees down and 3 degrees to the right. The little bumps on the lens are designed to work with the T-3 Safety-Aimer. We have no idea how this thing works, but here it is...

Trivia - Multi-Purpose Light

This cute little trouble light has a steel-backed automotive lamp, and a cigarette lighter power cord. Carry one of these around in the trunk of your 6-volt car.