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1973 CB350 Incandescent to LED Headlight mod.

GaryJames

Veteran Member
Joined
Jul 7, 2022
Total Posts
307
Total likes
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Location
Auckland, New Zealand
While searching the internet and the usual Honda Parts suppliers I have found a few who can supply a suitable LED Head Light bulb.
But at a price, usually in the USD $25 to 29 range. (some supply two for that cost)

Aliexpress ( yes I know, Chinese manufacturing and I try not to buy " made in China" ) has a multitude of LED bulbs at extremely reasonable prices. You can get the small BA9s that fit in the instrument cluster for under a $1 for two. 15mm headlight LED's that have a main and High beam can be had for only few dollars more.

The big problem is trying to identify the correct base.

Here is a picture of the standard Honda Incandescent Bulb:
CB350 Incandescent Bulb.gif

I might be wrong here but I see this as a BA15D ( or P15D ) base, ie, with two soldered pad connectors for main and high beam.
The "15 " part being the diameter in mm of the base.
The fitment is H4 which is the thin metal disc thingy going around the base with three sticky out bits.

Searching on Aliexpress I find these:


LED Headlight bulb CB350.gif

The correct base is the one on the right t but the correct fitment is the one in the middle with the disc and three sticky out bits.
However the base is an H4 so to fit in our old Honda's you will need an H4 socket and have to wire it into the loom.

Looking closely at the Incandescent bulb it seemed to me that the disc should be easily removable as it seemed to be held on with some dimples in the metal. Sure enough by wiggling it it came loose and I was able to slide it down and off.
The disc prongs are not equal distances around so that when inserting and turning the solder pads line up with same in the socket. I marked the base and disc before removing.

IMG_2229.jpg

Incandescent Bulb with mounting disc removed .

Now the LED choices have the same 15mm base. So I went ahead and bought a couple ( the right hand one in the picture ) of them from Aliexpress. at NZD$7.90 ( USD about $4.8 ) plus shipping i can afford to experiment.

When they arrived I removed the incorrect circular based on the LED and slid on the one I removed from the incandescent bulb.
Orientating it in regard to the double soldered connection pads at the bottom, and pushing it on to the dimple marks.

Inserted in the head lamp and turned it on but I had the orientation out so had to turn the disc around to next indent mark and it worked fine on L and H.

The thing with the LED bulb I bought is it has a focused round top that operates on H and projects a beam. Some just have a few LED's with no focus and they just spray the light forward and around.
I will re visit the H beam when it is dark one night to see what shape it is at a distance......

Also have to take a pic of the modified LED bulb which I will post presently.
It was relatively simple to do and saved me having to modify the Honda standard base for a wired in H4 type.

Cheers

Gary
Auckland
 
I found this for the PD bulb
P15d-25-1 is the bulb's base (formally called the 'cap'). P = prefocus, 15 = minor diameter, d = two electrical contacts, 25 = major diameter, 1 = variant.
 
Sounds right LDR.

As promised here the subsequent pictures with the LED fitted.

IMG_2234.jpg

Chinese supplied Headlight LED for motorcycles and ATV's...
You can see the pre focus round top.

IMG_2233.jpg

Fitted in the standard Honda H4 socket.

IMG_2235.jpg
Handle Bar with in the L position

IMG_2236.jpg

Handle bar switch in the H position.

I measured total battery current with points open and got 0.416 amps on "L" and 0.6 amps on "H"

That is a lot lower then the incandescent bulb.

Cheers

Gary
 
I've been looking for that same p15d-25-3 LED bulb here in the US because I like that short design and now you've verified that it has a true high/low function. That is a nice OEM socket. I have one similar for conversion from sealed beam which needs the reflector bowl cut with a hole saw and then notched, that I got from DrATV on ebay (Beatrice Cycle) but not sure they are still around or available. Good to know Honda had them on non-US market models. I would have liked to seen the back of your reflector bowl and it's opening out of curiosity.

I'm planning on doing a CB160 sealed beam that was designed for a 35-35 watt so those amperage figures should work for it. I can't remember the wattage for the 350, off hand, but seems like it's workable.

Thanks.
 
BB, will take a pic for you later this afternoon of the reflector reverse.
The standard Incandescent CB250/350 bulb is stated as 35/35 watts.
LED's are sometimes not quoted in Watts since I guess they consume minimal amps, but usually only Luminaries( brightness ) ...hence 4000k Lum's, 5000k lum's etc.
However the one I modified and fitted is quoted as 20W.

Cheers

Gary
 
BB, will take a pic for you later this afternoon of the reflector reverse.
The standard Incandescent CB250/350 bulb is stated as 35/35 watts.
LED's are sometimes not quoted in Watts since I guess they consume minimal amps, but usually only Luminaries( brightness ) ...hence 4000k Lum's, 5000k lum's etc.
However the one I modified and fitted is quoted as 20W.

Cheers

Gary

Awe, Gary, I didn't mean for you to take it apart again. :) I just thought it cool that Honda had an OEM replaceable bulb socket and matching reflector. I will probably use my aftermarket conversion socket from DrATV, they made these available to the CT90 crowd, who blow sealed beams a lot more frequently due to those puny 6volt batteries.
Thanks for the wattage confirmation, both 160's and 350's are the same then.
I see LED ad copy that seems to suggest they put wattage figures as an equivalent to an incandescent, rather than the actual draw. 20 watts that yours specifies should be about right for both our systems.

Also see the "k" figures, but this should be in reference to the color temperature of the light and is degrees Kelvin (white, daylight, bright white). Lumens (lm) is the quantity of light similar to candlepower.
For instance, I have another LED bulb that draws 25 watts and is rated at 2600LM and 6000K (Xenon white) that I will be using on my 305 Dream but it has an H4 base unfortunately and I'm not keen on trying to modify the 160 sealed beam to an H4 socket.
 
BB, here are the pics anyway. Maybe some ones else might make use.
Since I spent a few minutes dressing the b birds nest around into the rear of the shell it is quite easy to take the reflector off. Only two screws.


fullsizeoutput_2d50.jpg
Rear of my reflector. Standard focussed reflector for 1972/73 K4.

IMG_2253.jpg
The Honda OEM Bulb Socket with new P15D LED installed.
This is a better shot of the projection lens at the end when used on High Beam.

fullsizeoutput_2d52.jpg

Measurement of the reflector hole. There are two square cut outs of unequal width which dictate which way the socket goes in.

cheers

Gary
Auckland.
A very soggy Auckland with the second pacific origin rain band due to night. Red alerts sent to all cell phones an hour ago, all Schools closed for the week.
Plenty of flooding in the one last week, 4 drownings so far. one was an idiot canoeing down a open drain and got sucked into a covered culvert.
Water level got to within 1 1/2" of coming inside my rumpas room sliding door.
 
Thanks Gary. That is the same as my aftermarket conversion to p15d-25 socket. Thanks for the measurement too. I found that same bulb on the US ebay and ordered a couple.
I hope your deluge subsides soon. Keep your powder dry. (y)

The copy said 1600 lumens, not bad.
 
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