Lighting Question

[Mick Milakovic]

I was looking thorough my manual today and it says that the Penton headlight is 6V/35W and the taillight is 6V/4W.  I'v been running a Preston Petty front and rear light and the front bulb is a Westinghouse #4415 12V 5A and works OK but gets brighter and dimmer with RPM, but the rear bulb is an 1157 GE 12V/32W and does not work at all.  Front light is wired to the yellow wire and rear is wired to white.  I used to use this same set up on my Husky and it worked fine (with a Motoplat).

I'm setting up for the ISDTRR and I know I don't need working lights, I just want them. What do you guys suggest?  Thanks in advance,

Mick

[KJDonovan]

Mick,

Each of the power supply wires (Yellow, White and Green) are connected to a separate coils inside the Motoplat.  If your tail lamp is not working while connected to the white wire it's possible that particular coil is burned out.  Try connecting the tail light to the green wire coming from the Motoplat.  Also make sure there are no bared spots on the wire leading to the tail light that are grounding out on the frame.

Thanks,

Kevin

[Andreas Piepke]

Hi Mick,

As far as my wiring diagram is concerned the white wire isn't used. I isolated it's end. I distribute the power by means of a handle bar mounted switch. I am using a $15 three way switch with four wires from Flanders in LA. This way you can turn the lights off when starting the bike. I can tell you the color-code connections for this switch, if you decide to go this route (took me a while to figure this out). The green wire from the generator is used to power the stop light via the break light switch.
As far as trouble shooting connections is concerned: I use an external 6 V power supply and a volt meter. This way you can trace power distribution without having to run the engine. You can pull out connectors to find where connectivity is lost.
I recently bought a pack of 10 6 V combination tail and break light bulbs off eBay for $12.90. These can still be found and don't cost very much.

Hope this helps

Andreas

P.S.: Once you have the volt meter out, just measure the voltage on each of the three wires coming from the generator with the engine running. This way you can make sure you know what works and what doesn't.

'73 Penton Hare Scrambler
'73 Norton Commando
'77 Maico 440 GS

[Jason Rowland]

Assuming you've got the same system that allowed 40 watts for lighting, you're asking it to deliver 90 watts to lamps that want twice the voltage, and I doubt your stator coils are liking that one bit. I'd probably try to find 6v lamps at the proper wattage to retrofit, or if the system is outputting DC rather than the AC voltage, find a LED solution, since they're able to give more lumens per watt than the incandescents.  If you search for "par36 6 volt", you'll find a drop-in replacement headlamp. The par (parabolic aluminized reflector, with each number equaling 1/8 inch) series usually come in several beam types from wide flood through spotlight, so you can choose what suits.  Until the recent advent of moving lights and LED's for theatrical use, most of the lamps hanging over rock stars were par64's.  For the rear, if you can't locate a 6v/4w with the proper base to retrofit, maybe you can throw a 9v battery and some white LED's behind the (presumably) red lens?  I guess if there's a brake switch involved, a bit of wiring to change the voltage or number of LED's in the circuit wouldn't be too tricky.

[brian kirby]

Putting 12v bulbs in the 6v Motoplat lights was/is a common way to prevent bulbs burning out but obviously they will be dim. Even with the 6v bulbs they never really put out much light.

Brian

[Jason Rowland]

I try for 130v lamps for home use for the same reason...
There are par36 LED lamps that run on AC, but they're a pretty penny:
https://www.1000bulbs.com/product/112231/PLT-PAR369570060.html
I suppose it doesn't make much difference what filament voltage (6v or 12v) you use in this case, but not exceeding the power (wattage) rating of the power supply (stator coils) is the important part.

[brian kirby]

I have an internal rotor Motoplat on my 84 KTM125 so I will rig up a battery and a switch for the Reunion Ride.

Brian

[Mick Milakovic]

What if I wired both lights (head and tail) to the same yellow wire?  Is that a parallel series thus dropping the voltage to 6 to each light?  I know it will be even dimmer.....

Mick

[Jason Rowland]

If you wired them in parallel (stator coil into lamp one, out of lamp one to ground...stator coil into lamp two, out of lamp two to ground) you stress the stator coil more, as you are increasing the current and power required...brightness not affected. If you wire them in series (stator coil into lamp one, out of lamp one into lamp two, out of lamp two to ground) you decrease the current and power required, stress the stator coil less, and each lamp shares a portion of the 6 volts available, based on their wattage rating. If you used two 6v/20watt bulbs, they would both see 3v...brightness affected.  I'm assuming the output of the stator coil assigned to lighting duties to be 6v, as you mentioned your manual specifies 6v lamps.

[Mick Milakovic]

Thanks Jason, that makes sense.  Out of one bulb and into the other.  It won't be very bright but I wont stress the coils.  I might try that first then try to spend some money on lower volt and watt bulbs.

Mick

[Lew Mayer]

A Preston Petty LED wouldn't draw much.

Lew Mayer

[brian kirby]

Mick, your problem is not the 12v bulbs per se, but the relative wattage. The original circuits are 6v/35W headlight and tail light circuit is rated at lower power, 6v and 4 watts. An equivalent 12v bulb will be half the wattage of a 6v bulb so that would be 12v/17.5W for the headlight and 12v/2W for the tail light. You probably wont find 17.5 and 2W bulbs, but that will give you a good idea of what you should be looking for, something like 12v/18-24W for the headlight and 12v/5W for the tail light.

Wire them in separate circuits, not in series, that is the intended purpose of the separate coils in the stator. The 12v bulbs wont over stress the stator because they have higher resistance than 6v bulbs of the same wattage which results in less current draw, not more. In other words, a single higher wattage 12v bulb by itself in the circuit is the same as two smaller wattage bulbs of equal total wattage in series in the same circuit. The stator can not be over stressed like a power supply on electronics, the stator sends out whatever unregulated power it makes regardless of what load you put on it, which is why the lights are dimmer at idle and get brighter as the stator generates more power with more RPM. If the load is too low, like a bulb rated for 6v/10W on the 35W headlight coil for example, it will simply burn out the bulb but it will not damage the stator coil. Conversely, if you put too high a load with a 64W rated bulb, it just wont make it glow, but again, it will not damage the stator coil.

Even if your tail light was wired correctly, that 12v/32W bulb is the equivalent of a 6v/64W bulb. In other words, even if it was wired correctly that tail light bulb filament is so heavy the 4W Motoplat stator tail light circuit can not do more than maybe make it get warm, and surely not make it visibly glow. Even for the 6v/35W headlight circuit that bulb is double its power rating so it likely would barely glow if at all.

Brian

[Mick Milakovic]

Thanks Brian, maybe I had different bulbs back in the day.  See you in Combs.

Mick

[Kip Kern]

I use 12v bulbs with both wired to the yellow wire

[Andreas Piepke]

Mick,

have a look at eBay: http://www.ebay.com/itm/1154-STOCK-6V-TAIL-LIGHT-REAR-BRAKE-STOP-TURN-SIGNAL-LAMPS-BULBS-BOX-of-10-/310357967405?hash=item4842c6c22d:g:jaEAAOxyXHpSQ3Cw&vxp=mtr  these are ten 6 V combination tail/break light bulbs for $7.95. Perhaps my previous post wasn't clear: also when using a handle-bar mounted light switch, as originally done, the yellow wire powers both head and tail light via that switch. The green wire goes directly to the to the break light switch (not through the switch on the handle bar) and the white wire isn't used. I have this from the wiring diagram in the Penton Hare Scrambler manual. For the 6 V head light bulb: you can find these on eBay too (http://www.ebay.com/itm/Motorcycle-Headlight-3-LUG-Bulb-12v-35-35w-/401150086683?hash=item5d66688e1b).

Cheers

Andreas

'73 Penton Hare Scrambler
'73 Norton Commando
'77 Maico 440 GS