Honda Motorcycle Headlight Modification Page
(Reposted with kind permission of author Bob Peloquin; edited and updated to reflect current bulb information 11/04)

US motorcycle headlamp standards are badly in need of updating, for they permit motorcycle headlamps of grossly inadequate beam performance for safe nighttime riding. Honda equips many North American motorcycle models with special 45/45w bulbs that look like regular H4s, but aren't. Models using these reduced-wattage bulbs include the VFR, GoldWing Interstate, F6 Valkyrie Interstate, ST1100, and ST1300.

The solution is to modify the headlight assembly to accept standard H4 bulbs. Drilling, filing, and cutting the stock reflector are required so this job is not for the casual user. I suggest it be left to qualified individuals with the right tools and experience. If removing all your fairings doesn't scare you away and you've been looking for another use for that Dremel tool you got for Christmas, this job might be just what you need to take your mind off the snow-covered roads outside (well, there's snow on the roads outside MY window... grumble, grumble).

Here's an H4 and a Honda 45W/45W bulb for comparison. Note the H4 has its locating tabs closer together than the Honda bulb. Also note the tiny pins sticking up from the flattened bottom which engage a tab in the headlight assembly. Honda's are more widely spaced compared to the H4 bulb.  

You can really see the difference looking at the rear of the two bulbs, the Honda bulb uses 3 evenly-spaced locating tabs while the H4 uses much closer spacing between the two lower tabs. For reference, the special Honda 45/45w bulb uses a "PX43t" base, while the standard H4 uses a "P43t".  
Honda special bulb
 
H4/9003 bulb


The Old Way:

There is a simple way you can install a standard H4 (or 9003, or HB2) P43t base bulb in the stock headlight assembly using coat-hanger or a nail and bending/cutting the two side locating tabs to hold it in place. But, the base of the bulb does not sit at the correct depth in bottom of the reflector. This raises the angle of the bulb in the reflector resulting in having to adjust your headlights upward so much to get a good low-beam that when using high-beam all you do is light up trees and airplanes. The problem is illustrated here. There are also shim rings you can get from the likes of Electrical Connection, but these require the very difficult job of cutting off the H4's two lower tabs. They are made of very hard stainless steel, and cutting them almost always tweaks the bulb base (with manual cutting methods) or shakes the filaments to death (with power cutting methods). The method on this page offers a one-time, permanent fix that lets you install standard, unmodified H4 bulbs wherever and whenever you need to.

 

Tools & equipment you'll need:
- 10mm socket and ratchet (for removing mirrors)
- #2 Phillips screwdriver for Dzus-fasteners, trim screws and body clip removal
- Electric drill and bits
- Dremel Moto-Tool or equivalent
- High-speed steel cutting bits (sanding plastic just melts it into a mess, buy some cutters for this job)
- 2 new H-4 headlight bulbs

Modifications begin with removing the headlight assembly from the bike. You must remove the entire upper fairing, windshield, mirrors, etc. to gain access to the headlights. You should attempt this only if you are confident that you can do it without breaking anything in the process. Fairing parts are very expensive and easy to screw-up if you don't know what you're doing. Be warned. Here's a sample procedure for 1994-1997 VFR models; consult the applicable service manual for other models.

1. Remove left & right mid-fairings.
2. Remove mirrors and 4 screws from inner trim panels above dashboard.
3. Remove the windshield by lifting it off the mirror-mounting posts and wiggle it out of the fairing.
4. Remove 4 "push to release" clips from top of inner center fairing.
5. Unscrew and remove 2 body clips from center fairing and remove.
6. Remove 4 fairing bolts from upper fairing and slide forward slightly to gain access to wiring harness.
7. Release wiring harness from two clamps on gearshift side of upper fairing, unplug both headlights and turn signals.
8. Gently spread rear of fairing to get it past fork legs and place face-down on a soft cloth or blanket.
9. Unscrew 4 large Phillips-head shoulder bolts holding headlight into fairing.

After removing the headlight assembly, take the black rubber boots off and you'll see two bulbs in holders like this.  
Unlatch the spring-clip bulb retainer and remove the 45/45w bulb. Next, remove the two screws holding the spring-clip in place so you can place the new H4 bulb in place and mark the areas you'll need to cut. Note that you'll have to rotate the spring-clip clockwise to the next mounting boss to allow fitting the H4 bulb.  

You'll have to drill a new hole for the spring-clip hold-down screw. Caution, the plastic of the reflector assembly is very brittle. Use a 9/64 inch drill marking the depth with tape slightly deeper than the length of the hold-down screw. (It's a good idea to start the hole with a smaller bit to make it easier to keep the drill-bit from walking)

The areas you'll be cutting are shown here in red. Take care to keep the cut-out areas level with the original cut-outs so the bulb will sit at the proper angle in the reflector. The small areas of the center tab can be filed to allow the front tabs of the H4 to fit over the plastic tab on the bottom of the reflector.

 
Here you can see the high-speed cutter at work removing plastic in the marked areas. Special note here... The plastic used in the reflector is very brittle. You really must use a high-speed motorized cutter like the Dremel to avoid cracking the plastic. Also, plastic shavings will fly everywhere and get all over everything, including inside the headlight assembly. A small rubber ball or even a wad of paper towel or lint-free rag stuffed into the headlamp at the start will prevent an aggravating cleanup job later. If you forget and plastic chip do get into the headlamp, you'll have to wash it out with hot, clean, soft water and two drops of clear dishwashing liquid (regular Palmolive, regular Joy, regular Dawn, etc.—basically anything without hand lotion in it), then rinse with more hot, clean, soft water until there are no more soapsuds, shake vigorously to get the water out, and finish the drying job by putting the headlamp in the kitchen oven, turning it to Bake/350° for 3 minutes, then turning it OFF and leaving the lamp in the closed oven for a few hours. Do not fail to turn the oven off, or your headlamp will melt.  
When you're done, mount the spring-clip using the new hole you drilled and install the spring-holder in the reverse position from the original so you can clip the spring under the lower edge of it as shown. You will now be able to use regular H4, 9003 or HB2 bulbs. The standard relays & wiring will safely handle the 60/55 Watt H4 bulbs giving you a noticable increase in lighting capacity, and special higher-efficacy 60/55w bulbs can be installed for an even greater output. The best bulb presently on the market is this one. You can also use any of the multitude of "blue", "white", "silver", "superwhite", etc. type bulbs, if you want to go through all this effort to wind up with less light than you had before (all those types of bulbs are a scam).  

Photos and concept Copyright © 1999 Bob Peloquin (used by express permission) and this page Copyright © 2017 Daniel Stern. Thanks, Bob!