750 SF1 wiring for indicators

O

olly

Senior member
Two questions if that's ok please.

I'm looking in the 'green book' and the wiring diagram for the 750 SF1 with CEV plastic headlamp does not show there being a lamp in the instruments to show the indicators are flashing. Is that right?

The SF2 diagram seems to show two wires going to the 'flash' tell-tale lamp for the indicators. What prevents the current traveling down the other wire where it joins the tell-tale lamp and lighting up the indicators on the other side too?

Thanks
 
The current does travel down the other wire. That's how the circuit is made. The opposite (non functioning) side provides a path to earth for the wee little idiot lamp.
It earths through the filaments of the indicator lamps on the opposite side. But the current through the little 3W globe is insufficient for those lamps to illuminate. It's not possible for any more current to flow because the little 3W globe has a high resistance. It's analogous to an orifice plate in hydraulics - a kind of bottleneck in the system.

PS: Note that the current travels one way through the idiot light when the right indicators are on, and the opposite way when the left is on. So a LED won't work the same way because it's polarity sensitive. It only flows current one way. If you want to use a LED replacement, the simplest way to do it is to use two connected in parallel, but head to tail so one will light when the current is going one way, and the other will light when the current is going the opposite way. You could jam both LEDs in the same hole in the dash, or set them up as separate lamps for right and left. Obviously you'll also need a suitable series resistor with the LEDs.
 
Last edited:
Nup it was 76.
Why SF3s and triples had l/h gear changes.
Got my motodd 1200 registed as a 74 model.
Thought blinkers were required from about 1970. Was told id have to fit blinkets to the SFC if i ran it over the pits
 
I thought it was pre 75 from memory. I do remember the bollocking I got from a bike cop about not having 2 mirrors and blinkers on my 64 Bonnie though. Skinny people could do the right side arm out turn signal using their left arm. I could not. Leg signals helped
 
I think that the blinker rule varies from state to state. In Old I was told that from ´83 all bikes had to have them. Pre that, if the bike had no blinker switch it need not have them. I went through this with a 1982 off-road bike that a picky cop slapped an unroadworthy on for no blinkers, I had blanked off where the blinker switch was and said it had never had blinkers, and the rego office found the rule in their "bible" and cancelled the notice. The cop spewed because his mate had had the same model and it had blinkers, his superior just laughed at him, he must have been popular.
The theory doesn't need to be understood. Unless you are fitting LED blinkers, just wire it as you say with the wires going to either side of the meter lamp as per the SF2 diagram, it will work.
 
Tippie said:
The theory doesn't need to be understood.
Click to expand...
I disagree. If you want to work on your own electrical systems you should understand how it works. Otherwise you're just poking about in the dark and are more likely to cause further damage than repair anything.

There's no way I'd try to repair something if I had no idea how it worked - like my smart phone, which works by magic as far as I can tell.
 
You must log in or register to reply here.
Back
Top