slmjim
Hopeless Tool Junkie
- Joined
- Jan 16, 2011
- Messages
- 175
- Bike
- Which one today...?
The purpose of this post is to (hopefully) assist others in their inaugural headlight bulb replacement. It's a record of my experience and, perhaps more importantly, I've endeavored to gather into one thread all the resources I used to make the bulb replacement process as simple as possible. There is also a brief discussion of OEM Honda bulbs vs. standard H4 bulbs. Thanks to the resources of this forum, bulb replacement was pretty straightforward.
I chose to install a new OEM bulb (instead of a H4) and also purchased a spare.
The first issue I'd like to address is the differences between a standard H4 bulb and the OEM Honda bulb. I keep a small inventory of H4's, because they fit our '93 CB750 Nighthawks and the Kawasaki Z-1's in which I've installed aftermarket Halogen headlight assemblies. There are two physical differences that I've been able to ascertain:
1)The positions of the tangs. The pic of the two bulbs side-by-side clearly show that the tabs that are at approximately 4 o'clock and 8 o'clock are angled differently between the two bulbs. The bulb on the left is OEM Honda. The bulb on the right is standard H4. Also note that the top 12 o'clock tab on the OEM bulb is slightly wider than the standard H4.
2) Not as apparent, and difficult to photograph, is the fact that the glass body of the OEM bulb/filament assembly is rotated slightly clockwise on it's vertical axis, relative to the 12 o'clock tab, because the rectangular cutout in the steel base where the glass enters the base is, also, so rotated, pointing to about 1 o'clock and 7 o'clock. The two new OEM bulbs and the one I removed from service all exhibited this rotated orientation. All of the H4 bulbs I checked were true to the 12 o'clock/6 o'clock orientation. The result is a slight clockwise rotation the bulb/filament assembly relative the flat in the steel base.
Why the rotation? My best guess is to modify the resulting beam patterns. It'd probably be a subtle difference, but we all know how, uummm... precise mama Honda likes to be about such things.
But...
If we look at the bulbs as installed in the headlight assembly, we see that the flat in the hole of the reflector in which the bulb base seats is not oriented exactly plumb horizontally. It's rotated slightly CCW relative to horizontal, resulting in the bulb/filament assembly being returned to the 12 o'clock/6 o'clock orientation relative to plumb vertical! This would seem to negate the need to have the bulb/filament rotated in the base if the flat in the reflector hole had been exactly plumb horizontal to begin with. It would also cause a standard H4 bulb to be rotated slighty CCW relative to vertical (11 o'clock/5 o'clock). I don't know what, if any, noticeable effects this may cause in the resulting beam pattern. If anyone has an explanation of the bulb/hole rotation I'd like to hear it.
The second issue is, why does it often seem to be the left bulb!?! In my lurking of this site over the years I remembered seeing that question a few times, so some searching led me to this thread. It's a fairly deep thread and somewhat technical, but in a nutshell the circuits for L and R filaments are slightly different, leading to slightly higher voltage being applied the the L bulb. There is also a mention that the high beam filament is rated at ? the life of the low filament:
https://www.st-owners.com/forums/showthread.php?62641-ST1300-Headlight-Wiring-Diagram
This next thread explores installing a 20 watt wire wound resistor of very low resistance (0.5 ohms) in the ground wire of the left headlight bulb, to slightly reduce applied voltage:
https://www.st-owners.com/forums/showthread.php?121599-Mysterious-Left-Headlight-Burnout-Simple-Fix!
How to replace the bulb:
https://www.st-owners.com/forums/showthread.php?84492-How-do-you-replace-a-ST1300-headlight-bulb
http://www.hard-core-ware.com/howtos/index.php?page=headlamp
And
http://www.jfheath.co.uk/st1300/st1300-serv-headlight.shtml
I was able to release the connector from the bulb by kneeling at the left side of the bike, facing forward, and reaching up from underneath with my right hand. Once the connector was off, I stood next to the bike, again on the left side and from above removed the rubber ring, then released the spring retainer clip that secures the bulb into the holder. I used rubber surgical gloves to simplify handling the new bulb while inserting it into the holder, so as not to touch the glass body of the bulb. After that, assembly was in reverse order. The removal of the connector and retainer clip sounds simple, but in reality they're not intuitive, at least to me. Once I got the knack, it was indeed easy.
So there we have it. Please feel free to post your experiences, tips, tricks or corrections.
Good Ridin'
slmjim
I chose to install a new OEM bulb (instead of a H4) and also purchased a spare.
The first issue I'd like to address is the differences between a standard H4 bulb and the OEM Honda bulb. I keep a small inventory of H4's, because they fit our '93 CB750 Nighthawks and the Kawasaki Z-1's in which I've installed aftermarket Halogen headlight assemblies. There are two physical differences that I've been able to ascertain:
1)The positions of the tangs. The pic of the two bulbs side-by-side clearly show that the tabs that are at approximately 4 o'clock and 8 o'clock are angled differently between the two bulbs. The bulb on the left is OEM Honda. The bulb on the right is standard H4. Also note that the top 12 o'clock tab on the OEM bulb is slightly wider than the standard H4.
2) Not as apparent, and difficult to photograph, is the fact that the glass body of the OEM bulb/filament assembly is rotated slightly clockwise on it's vertical axis, relative to the 12 o'clock tab, because the rectangular cutout in the steel base where the glass enters the base is, also, so rotated, pointing to about 1 o'clock and 7 o'clock. The two new OEM bulbs and the one I removed from service all exhibited this rotated orientation. All of the H4 bulbs I checked were true to the 12 o'clock/6 o'clock orientation. The result is a slight clockwise rotation the bulb/filament assembly relative the flat in the steel base.
Why the rotation? My best guess is to modify the resulting beam patterns. It'd probably be a subtle difference, but we all know how, uummm... precise mama Honda likes to be about such things.
But...
If we look at the bulbs as installed in the headlight assembly, we see that the flat in the hole of the reflector in which the bulb base seats is not oriented exactly plumb horizontally. It's rotated slightly CCW relative to horizontal, resulting in the bulb/filament assembly being returned to the 12 o'clock/6 o'clock orientation relative to plumb vertical! This would seem to negate the need to have the bulb/filament rotated in the base if the flat in the reflector hole had been exactly plumb horizontal to begin with. It would also cause a standard H4 bulb to be rotated slighty CCW relative to vertical (11 o'clock/5 o'clock). I don't know what, if any, noticeable effects this may cause in the resulting beam pattern. If anyone has an explanation of the bulb/hole rotation I'd like to hear it.
The second issue is, why does it often seem to be the left bulb!?! In my lurking of this site over the years I remembered seeing that question a few times, so some searching led me to this thread. It's a fairly deep thread and somewhat technical, but in a nutshell the circuits for L and R filaments are slightly different, leading to slightly higher voltage being applied the the L bulb. There is also a mention that the high beam filament is rated at ? the life of the low filament:
https://www.st-owners.com/forums/showthread.php?62641-ST1300-Headlight-Wiring-Diagram
This next thread explores installing a 20 watt wire wound resistor of very low resistance (0.5 ohms) in the ground wire of the left headlight bulb, to slightly reduce applied voltage:
https://www.st-owners.com/forums/showthread.php?121599-Mysterious-Left-Headlight-Burnout-Simple-Fix!
How to replace the bulb:
https://www.st-owners.com/forums/showthread.php?84492-How-do-you-replace-a-ST1300-headlight-bulb
http://www.hard-core-ware.com/howtos/index.php?page=headlamp
And
http://www.jfheath.co.uk/st1300/st1300-serv-headlight.shtml
I was able to release the connector from the bulb by kneeling at the left side of the bike, facing forward, and reaching up from underneath with my right hand. Once the connector was off, I stood next to the bike, again on the left side and from above removed the rubber ring, then released the spring retainer clip that secures the bulb into the holder. I used rubber surgical gloves to simplify handling the new bulb while inserting it into the holder, so as not to touch the glass body of the bulb. After that, assembly was in reverse order. The removal of the connector and retainer clip sounds simple, but in reality they're not intuitive, at least to me. Once I got the knack, it was indeed easy.
So there we have it. Please feel free to post your experiences, tips, tricks or corrections.
Good Ridin'
slmjim
