t500 headlight bulbs

[Eric P]

So, I tried searching all over the net to find the headlight bulb that I needed for my 1971 T500. I came to the conclusion that I must have a sealed beam because of the lack of information. Well, luckily this isn't the case!

My T500 had two bulbs in the headlight assembly. I pulled them out to replace them. The high/low beam bulb, which says "3251A12V35/25WL" and the parking lamp which says "STANLEY.12V3.4W". The parking lamp is an easy replacement it's simply a 12V 3.4W bulb with a BA9S base. They're used in lots of instrument panels, so they're all over the place. The headlight bulb is kind of strange. It's a double contact prefocus base with 35/25W filaments. Easy right? Wrong. Somebody please correct me if I'm wrong, but the bulb appears to be long since discontinued. The closest bulb I could find is an A5676 bulb. This is a 35/30W bulb. Not too far off, and it has the correct base, but not exactly original. Here are a few pics of the bulbs that came out of my headlight:

Parking lamp:


headlight:




I'm planning on un-soldering the flange from the headlight bulb and soldering it to a new bulb to try to upgrade without changing the original reflector and bulb holder. I ordered a pack of A5676 bulbs. I'll post up an update when they come in to verify that they work. Hopefully this can help somebody out in the future.

Eric

[akendall1966]

Hi EricP

I saw your post on sealed beam headlights and assumed you must have a different headlight to me. I have have a similar issue with availability of the main bulb, so have been working on this as my solution....

I started with this http://www.wemoto.com/parts/picture/hl-770005/

The trimmed off the flange...

Made up an adapter ring...

Fitted together...

now can used any BA20d fitting lamp which are still common usage on bikes (inc LEDs)



Just waiting on some rubber channel I ordered to show up to make up a part to hold the thing in place. The holder I modified even has a nice rubber cover the works with the reflector. So hope to be ready to fit in about a week once the businesses here get back to normal after the holiday period and the rubber channel gets shipped.

I have only done a quick test, but did find rotating the bulb relative to the reflector changed the beam pattern quite significantly, so you might want to try this before final soldering to get the best result.

Of course still have the old holder and rubber so fully reversible modification too.

Cheers
Adrian

[Eric P]

Adrian, that looks like a really clean solution. Did you include any sort of design to make sure the bulb lines up correctly and doesn't twist in the reflector? The stock bulb can only go in one way due to a notch in the bulb holder that lines up with the pin on the reflector. Does the beam pattern of the new bulb compare well with the old bulb?

If that works well for you, are you interested in selling one or two of those adapters? It would be nice to be able to use an easy to find bulb in case the headlight blows while I'm out riding. I bought a case of bulbs, so I should be set for a while, but carrying spare bulbs doesn't always work on a bike. If you're interested, I can mail you one of the bulbs I found so you can see how they compare to your adapted bulb.

I'm just amazed this topic hasn't been brought up before, at least that I saw.

[akendall1966]

Hi Eric

Haven't tested properly yet until I get the rubber channel to make the fixing part. If this holds it secure enough I might just mark the position relative to tang on the reflector if I find it moves I'll drill through the holder and reflector flange and use a pin to set the position. Which would still allow the old holder go fit.

I am not really tooled up to produce in batches myself, so would have to farm it out which needs demand to be economic. Let's see how it all pans out if it works to a good enough standard I could do you one as a favour.

P's the ba20d is as 20mm diameter base where from memory the standard bulb is closer to 15mm diameter bayonet same as a regular tail light bulb. The fitting I used works with S2 style automotive bulbs.
AK

[Zunspec4]

Hi Guys,

Pretty sure the T500 headlight bulb is available in the UK, or they were when I bought 2 or 3 a couple of years ago. I will do some searching and see what I can find. 35W is rather feeble but then the T500 charging capabilities are modest too .

Cheers Geoff

[jabcb]

Wow, a nice bit of work there — way beyond my skills.

Some years ago I upgraded my T500 to a modern rectifier/regulator + AGM battery.
Also have been using a 45/45W headlight without any problems.

[akendall1966]

I have seen them eBay at extortionate prices over 20 quid, discount bike spares has the GT bulb but looks like a different flange but I haven't seen the early lamp at sensible money. I went with S2 style as they are available 35/35 (my ccm trail bike is 35/35) and 40/45 plus some LED options. I too have modernised the wiring and gone to a modern rec/reg.

So hopefully can get acceptable lighting out of the meager alternator.

AK

[tricky1962]

There is one currently on the UK ebay for £6 + postage

http://www.ebay.co.uk/itm/NEW-GENUINE-S ... Sw9mFWIRDm" onclick="window.open(this.href);return false;

I'm running the same wattage using the standard regulator and recitifier with no problems

[Eric P]

The A5679 is a 45/45w bulb. I almost ordered one, but I wasn't sure that the charging system could keep up as I'm not overly familiar with this bike. On my Yamaha (sorry), a higher wattage bulb than stock would drain the battery and leave me stranded. Can a t500 charging system run a 45W bulb without upgrading the regulator and rectifier?

[ConnerVT]

Can a t500 charging system run a 45W bulb without upgrading the regulator and rectifier?

The answer to that is... Maybe.

The difference between a 35W and 45W bulb is about 0.85A of additional continuous current that the charging system needs to provide. A brand new T500 probably would fare well. But there are a number of factors which will affect if your bike will tolerate it:

-- Battery - A new, fresh, quality battery should handle supplying power as needed, and accept a charge when available. A questionable battery may not last as long.

-- General condition of wiring - Every connector adds to power lost in the charging system (they act like little resistors added to the system). So the condition of the wiring harness has a great impact. Also, the T500 charging circuit is switched by the headlamp switch on the handlebars (switches in the majority of the charging circuit), so the condition of this switch, as well as the wiring to the switch, has a potential for power loss.

-- Riding style - If you are a spirited rider, you will be running the engine at higher revs (on average) vs. lugging around town in high gear.

-- Headlamp always on - If you only have the headlamp on at night, obviously no issue. If you are (like me) in a headlamp always on locale, then you may want to bypass the headlamp switch charging circuit wiring (mentioned above), as stated HERE on Page 17. You will need to always have your headlamp on in this case, else you will overcharge your battery.

[tricky1962]

As I said, I'm running that wattage with no problems on a standard 44 year old set up (newer battery of course).

The battery seems to start charging at about 2500 rpm and I use the bike for a 10 mile each way commute, half in town and half at about 50-60 mph. Initially I made an effort where possible, to keep the revs up but since the spring haven't bothered.

I have the headlight on all the time.

The only mod I have made is to switch the rear light for an LED to reduce the power consumption.

These changes were made in October 2014, and so far so good.

Edit - Conner's post was added as I was busily typing. We seem to be basically in agreement I think.