R75/6 Electrical problem

[wirewrkr]

Okay let's make this really simple.
Electrically KEN, the 75 and 76 bikes are identical.
His bike is a 74 so that's a bit different from ALL the other post 70 airheads.
It's got a lot of weird 1 year only stuff in there. Including the ignition switch.
No one has yet explained the proper way to diagnose electrical, so let's start.
Sit down in front of the bike on a nice comfy roller seat or stool.
Remove the headlight insert. Yours originally came with a pop out style (and pop out they would!), but many have been upgraded to the screw style rim.
Either way, remove it, unplug the plugs off of it and lay it aside.
On the right side of the bucket as you look in to it, you will see the back side of the ignition switch.
When diagnosing major cut and dried failures always start here. In the center of the switchthere will be one or two large red wires. These (or this) is terminal #30 which ALWAYS indicates direct uninterrupted POSITIVE battery current.
Apply the multimeter or VOM or test light to this terminal to ascertain that you indeed have current.
YES? excellent. Now reach over and turn the key to the normal run position. This should apply current to at least the #15 IGNITION circuit, which is normally green on your bike. NO? Okay, with the key still on gently wiggle the contact plate of the switch (the part with all the wires plugged in) does the light flicker?
The switches get loose sometimes, will loose contact or just fail altogether.
This is very common with these switches, keep in mind it's almost 40 years old! There is a simple fix.
Any way, the main point to all this, is that since the switch is the first major distribution point for the electricity, start there. Always.
If you don't start with the basics, all the other tests are moot.
If there's no positive juice at the switch, then get your schematic out and start working backwards.
I think you'll find that these are WAY simpler than Triumph electrics.
wirewrkr
http://www.wirewerkes.com

[xpab]

So I went through every connection and everything looked good. Finally just decided to try switching out the battery and the bike turned right on. Once the battery was unhooked from the terminals, it was reading upwards of 16 or 17 volts. I have an odyssey and I'm guessing my regulator is fried or something of the sort and overcooked the battery. Going to try and get a new regulator in there tonight and make it up to rhinebeck for the weekend.

Can't thank you guys enough for all the help.

[Ken in Oklahoma]

So I went through every connection and everything looked good. Finally just decided to try switching out the battery and the bike turned right on. Once the battery was unhooked from the terminals, it was reading upwards of 16 or 17 volts. I have an odyssey and I'm guessing my regulator is fried or something of the sort and overcooked the battery. Going to try and get a new regulator in there tonight and make it up to rhinebeck for the weekend.

Can't thank you guys enough for all the help.

I'm glad your problem is solved. But the above doesn't ring right. I can't imagine any battery, upon disconnecting the battery, jumping up to 16 to 17 volts. If the battery was capable of 16 to 17 volts it would have been capable of lighting your instrument lights. Also a lead acid battery, which the Odyssey is albeit a fancy lead acid battery, will read perhaps 14 volts fully charged. Are you reading that 16 to 17 volts with the battery hooked up in the bike and the bike running? If so that would suggest a voltage regulator that has failed and running the alternator wide open.

Before you leave for that trip be sure to measure the voltage, at the battery with a DVM or similar meter. The volt meter on your bike is inherently inaccurate and actually measures the voltage in you headlight shell, which will be a lower voltage than at the battery.

I would run the bike at 2,500 rpm thereabouts and see what the voltage at the battery says after several seconds. I would expect to see about 14 volts if the battery is already well charged. A voltage reading that doesn't hit at least 12 volts will mean that something may still be wrong with the charging system or that the battery isn't fully charged. A voltage reading of 16 or 17 volts will mean you are overcharging the battery and you're going to end up harming the battery. With a new voltage regulator though, I wouldn't expect that to happen.


Ken