What bulbs to use after 12v conversion on 2-stroke

[Arthur Freeman]

Hi from Australia,
I have been given a Boyer-Bransden electronic ignition kit and will put it on one of my bikes (may be Leader or Arrow).
The conversion to 12volts using a Power Box (Rectifier/Regulator) seems straightforward enough (joining the Black/Green and Green/Yellow wires from the alternator into the input to the Power box) and replacing the points/condenser and back plate.
Now the interesting part arrives!. Our alternators (being Lucas RM13 or RM15) are fairly early versions and only put out about 50watts. Over the years (and specific to a 6 volt system) I have heard that it is not a good idea to change the headlight bulbs (6v 30/24) for the more powerful bulbs (6v 50/40 etc..) which were available - on the basis of the low output from the alternator.
So 2 questions - what bulbs have been used when converting an Arrow to 12volts?; and can advantage be taken in using LED "bulbs" (for any or all the existing lights)?.
Thanks, Arthur
By the way, I also intend converting another of the bikes with a Pazon 12 v set up!

[john.nash]

This is not really anything to do with two-strokes.

Putting large wattage headlamp bulbs in or adding stuff like hotgrips is liable to exceed the alternator output and slowly drain the battery.
I think these bikes are coil driven, which is going to leave you stranded.

Basically you need add up the wattage of everything on the bike. You will need include the ignition system in that.
This needs to matched to what the alternator is putting out.
Moving from 6v to 12v effectively doubles your watts (watts being equal to voltage x current).

What LED bulbs bring to the party is very, very low power usage.
Thus if you replace all your speedo, pilot, rear and brake lights with LED's then they will effectively "save" you watts. This would allows you to use a larger headlamp bulb.

Here's my Ariel example.
E3L dynamo. 8.5 amps at 1850-2000 r.p.m at 7 volts, which is around 60 Watts (8.5 x7) on a 6v system.
Headlamp bulbs are 25w, rear light bulb is 5/21W (tail is 5W, stop is 21W), speedo bulb is another 5w. Which makes 35W. Easily under.
You will see the ammeter move when you hit the brake or horn.
You could probably go to a 35W headlamp bulb (another 10W) but not a 55w, as at that point the dynamo cannot keep up and the battery slowly drains (and a little 6v battery doesn't have much in it).

If you replace the speedo bulb and the tail with LED, which use very little power, then you could easily use that 35W headlamp bulb with no bother.

[Eero.Korhonen]

You can also change LED bulb to headlight, but I think it is not legal.
But anyway, you get very bright light.
-Eero

[charles.bulloch]

You can get 35/35 watt QH headlamp bulbs from ebay. Cheaper than the usual alternative. Paul Goff's LED stop/tail light saves a few watts.

Charlie

[bh.sprint]

Hello,

I changed my Leader to 12 volts over 12 years ago ( Boyer power box ) and also use a Boyer ignition.
The bike has the larger rotor, its a 1965 model, which I am told gives a few more watts ( 55 ? )

I use a 40/45 watt bulb in the head light and the alternator seems to keep up with the demand OK.

I tried an LED bulb in the rear light but was not sure how good it was so reverted to the 5/21 watt .

I use an LED bulb in the speedo which saves a small amount of power and also use an LED riding light in the parking light, which seems quite bright.

On the MK 2 Leader 270 cc I'm using a 10 amp alternator so I can use a bigger head light bulb.

Brian.H.