Blowing Headlights

[Ben]

Having an issue and cannot seem to find a wiring diagram for a 1975 RV125, others do not entirely match....

Issue: Blows headlights, pilot light, taillight (not brake, powered by battery I assume) - over 6v delivered when revved

I have a rectifier (new), resister (condition unknown), and no regulator.... I also have a un-terminated Yellow/Red wire, Green/White under the seat.

Safe to assume I need a regulator and that it plugs into Yr & Gw under the seat, even though I cant seem to place one in the wiring diagrams I have seen?

I stumped as to why I am even getting current to blow the bulbs without a regulator being present to complete the circuit? ( under the seat the Gw has a male and female bullet connector splice which I have joined together, perhaps this is completing the circuit and I am delivering unregulated current directly to the bulbs?)

Any help appreciated, much thanks

[Zunspec4]

Hi Ben,

I have a 1978 TS125C which also has direct lighting a.c.(6v bulbs). These have also blown and I have been told that you need a good battery, receiving it's crudely rectified charge (half wave) to stabilise the a.c somewhat. My problem raised itself when my 6v battery became a bit dodgy (through lack of use I think) so there might be some credibility to this theory.

Cheers Geoff

[jabcb]

The wiring diagram for the 77 RV125 is here: viewtopic.php?f=29&t=4743&start=10

The wiring diagram shows an AC voltage regulator.
It shows the regulator connecting to a B/W wire -- this looks to be typo in that the wire is also labeled Gr.

Paul Miller lists NOS Suzuki regulator on eBay for $79: http://www.ebay.com/itm/Suzuki-RV90-RV1 ... 0874289219

Would expect a new aftermarket 6V AC voltage regulator to be better than the old NOS part, but its not easy to find it.

Looks like Rex Caunt has one for about $40
http://rexcauntracing.com/pages/regulators.html
http://www.ebay.com/itm/YAMAHA-XT500-DT ... 0165796372

[Ben]

I have current under the seat Green/white that is delivering unregulated current, 10v to 30v depending on rpm.

I'm not electronically inclined but building my own regulator sounds like cheap fun.

Of the tutorials I have found, reference is made to the regulator delivering up 7.1v and some number of amps. No mention of watts. I thin my headlight, pilot light, taillight and guage backlight all come from this source. Headlight is 6v 25w/25w .....any tips on how to calculate amps required?

[jabcb]

The max depends on the alternator performance output curves.

Examples for the triples are shown on page 18 of: http://www.ozebook.com/compendium/suzi/suzidata1.htm
The curves shown are for a 14V (DC measured after the rectifier).

Alternators have a maximum output for a given voltage.
You could do some testing to estimate the curve for a voltage that is safe for your headlight.

Alternatively, if you total up the watts of load that should give some insight.
Normal load is just the headlight + taillight + speedo light + battery charging.
(The magneto is separate & not part of the alternator load.)

There are two design considerations:
1) the electrical components must meet the voltage & current requirements
2) the regulator coverts the excess power to heat & you need a heat sink to prevent overheating of the electrical components

Considering how expensive & hard to find the headlight is, I would be inclined to just use the
Rex Caunt or Suzuki NOS regulator.

[Ben]

jabcb., appreciate the help. I have looked over a lot of wiring diagrams and I still cant make sense of it.

the only wiring diagram I have seen that comes close to what my bike is, is the RV125B, but its not entirely consistent and some of the icons I cannot decipher (RV125B Wiring Diagram).

Anyways, I have a

Y/R female open end = from lighting coil
G/W female = from charging coil
G/W male = ?? to/from ??
G female = ?? to/from ??

If you follow the Yr in the wiring diagram link above it turns into Gr (gray) then B/W which goes to the regulator....strange
And I cant decipher the G/W circuit either....


Anyone with a 1975 that can confirm whats what?

[ConnerVT]

It is a resistor.

RESISTOR ASSY, MAGNETO K,L
36500-27690

http://www.suzukipartshouse.com/oempart ... 54/magneto

[jabcb]

For the 77 RV125B wiring diagram:
The regulator wire that starts out Gr (gray) & switches to B/W should be typo. I would expect it to be Gr & not B/W.
If you look closely at the NOS regulator that Paul Miller has on eBay, it has two wires: a gray wire & a black wire with the grounding connector.

The resistor in your pic is shown in the RV125B diagram as connected to Y/W & G/W wires.
The G/W wire goes to the ignition switch & then isn't used for anything.

I may have found a wiring diagram for an earlier RV125 in this tread on another forum:
http://www.2strokeworld.com/forum/index ... ic=20322.0
The diagram is:

Looks to be a gray scale scan of a color diagram, which makes it harder to use.

The earlier diagram shows a different ignition switch & no voltage regulator.
It shows that the resistor is used as a substitute load when the lights are off.

Would seem reasonable that the early RV125 did not have a voltage regulator & the later models did.
That is what Suzuki did on the GT250.

Since the two diagrams are quite a bit different, you should definitely consider getting a RV125 shop manual that covers your model year. Check eBay.

I would also get an aftermarket AC regulator & mount it so that the frame (or something else) acts as a heat sink.

These mixed AC/DC wiring diagrams are certainly more confusing.
Looks like it confused the Suzuki engineers to the point that they included the resistor on the RV125B even though it is never used.