Originally Posted by Hmblrastafarian
1960 5ta that i built into a bobber.
Do i just turn the idle higher until it wont die with the lights on?
Short answer: no.
Longer answer: if you do that, the idle will be so high, it'll be difficult to to get neutral at a stop, and you'll 'crash the gears' trying to get it back into gear to pull away; raising the idle is treating a symptom, not the cause; the cause
is the alternator doesn't produce enough at idle to run even just the ignition on its own, never mind lights as well.
Does the bike have LED 'bulbs' in the lights; if not, as "tridentt150v" posted, their low current consumption compared to normal incandescent bulbs will lower the rpm where the alternator is
spinning fast enough to generate enough to power both ignition and LED 'bulbs'.
What alternator is on the bike? 3-phase high-output will produce the most at low rpm.
But the bike's problem is trying to run it on public roads entirely batteryless, Simply unnecessary at the end of the second decade of the 21st century.
EI? BB needs a minimum of around 10.5 volts to run,
Not necessarily. While most
Mk.4 will usually
run 'normally' at lower Volts than Mk.3, any given figure isn't guaranteed. It's 12V
electrics, not some imaginary figure somewhere below 12V.
Plus, again, it's trying to 'fix' the problem
by 'treating' just one of its symptoms. The problem
is the alternator doesn't produce enough Amps
at tickover/idle to run both ignition and lights. That's why Triumph fitted a battery with DC electrics, to power the electrics when the alternator can't.
Your tail light setup will draw up to 25 watts,
<img src="https://www.triumphrat.net/images/smilies/huh1.gif" border="0" alt="" title="Huh!" class="inlineimg" /> You're thinking of an incandescent stop/brake lamp/filament, which consumes 21-23 Watts (~2 Amps). I suspect the OP doesn't ride around with the stop filament illuminated all the time (or, if he does, that's part of the bike's problem). Incandescent tail
filaments consume 5-6 Watts (~0.5A).