about voltage regulators

 My friend has this this XL350 - the submarine bike
He bought his bike without lighting electrics, bike has only minimum
wiring to fire spark plug.
He wants lights. A headlight at least. His bike has three yellow wires
coming from magneto, just like most four stroke bikes I've seen. On
mine, three yellow wires goes to voltage regulator, and from it comes
a black and a red wire. Red= +12v, black = -12v. The question is, can
I use any voltage regulator or I must find the hard-to-find XL350
regulator? If not, why?

thanks!

-- Tiago

 

You can probably get away with another Honda three phase voltage
regulator/rectifier. It's probably worth a look at some Honda street bikes.
http://www.4strokes.com/tech/honda/images/XR650L_wiring.gif  

 
bikes.http://www.4strokes.com/tech/honda/images/XR650L_wiring.gif


Hey, Dave. I'm a regular over there- you a poster or a lurker?

DDave

 

Neither really, google led me there with the phrase "XR650L wiring diagram".
I've only owned one four stroke bike. It was a 1966 Honda S90 that was
subjected to a lot of experimentation.

 Tiago Rocha wrote:

Any old motorcycle 3-phase 12 volt regulator/rectifier should suffice as
long as the regulator's power capacity is at least that of the XL-350's
stator. The reason is that these R/R's regulate by shunting the excess
back into the stator. "Shunt" is a polite way of saying "short" without
setting off alarms with your clueless boss.

Then again maybe you should double-check and verify the XL350 was 12V.
Many old Japanese motorcycles were 6V. If it was 6V you could probably
get 12V out of it, the open circuit voltages on those yellow wires may
be as high as 70VAC.

By running a headlight you take some of the heat load off the regulator.

KTM (and likely others) have a single phase "lighting coil" and run the
headlight off the input to the R/R rather than the output. This is said
to be AC (which it is) but it mostly resembles very noisy DC. The R/R
still regulates the headlight voltage but does so by shorting when the
input exceeds the regulation voltage. In the bad old days headlight
voltage was not regulated when a lighting coil was used. So brightness
varied (a lot!) with engine speed.