Topic: Electrical gremlins are attacking!!

[Gordon]

750K1:  Electrical changes from stock are Dyna-s and Dyna 5ohm coils, H4 headlight, truck horns run through a relay connected directly to battery, heated handgrips (not used much recently), and aftermarket blade-style fuse holder.  All of these have been installed for at least two years. 

Now for the gremlins!
With the headlight off, bike runs and idles fine.  With headlight on, bike idles poorly and hesitates and sputters on initial accelleration, until it gets over 2K rpm, then it's fine.

So I'm thinking my battery is running down because it's fine over 2K when the charging system is making enough juice.  Nope, hooked up charger, it's at 100%, electrolyte levels all full. 

I disconnected the horns and the handgrips to narrow it down, still no change. 

The only thing I did to the bike before this happened was remove the tank to polish up the valve cover for the bike's Spring cleaning.  I checked all the wires and connections in that area to make sure I didn't snag something.  All seems fine. 

This happened very suddenly and during a time when the bike has been in regular use, so I don't think it's something that crept up slowly and I just didn't notice.  This leads me to believe it's either a loose connection or short somewhere, but I can't find anything.

Any ideas?  I'm going back out to the garage, but I'll check back in shortly.

[JohnG]

first thing I would do is install an ammeter on the bike and keep track of the flow (charge or discharge) under various conditionis.   I have an old british one from a Norton. It only reads +/- 6 Amps which is plenty.

Do NOT have  the ammeter measuring the amperage when the starter is on. Make sure and exclude that!

[Gordon]

Update:

After fixing a pesky stuck float valve on #3 carb, I got back to the electrical problem.  I hooked up my cheap digital voltmeter to the battery to see what was happening when I turn on the headlight.  Battery at rest is showing 12.5 volts.  At idle, with nothing turned on, it's reading a steady 14.5 volts.  With either the headlight or turn signal turned on, it drops to around 12 volts, and the engine starts to cut out. 

When I turn off the lights, the engine continues to labor and battery stays at around 12 volts until I blip the throttle, and volts go back up and engine idles fine until I turn something on again. 

Could this be a battery problem?  I know it's possible for a bad battery to seem fine, but then lose it's grunt as soon as a load is put on it.  This battery is only about two years old, but with the electrical additions I've made, I wouldn't be surprised if I killed it already.

[bryanj]

Its fairly normal as these bikes DO NOT CHARGE below 2-3,000 RPM and a battery is not fully charged at 12.5 volts its fully charged at 13.2 volts

[kslrr]

Almost sounds like a combination of things. First a short somewhere in the light/turn signal wiring that sets off the problem and then maybe a faulty regulator which can not recover, though you say the battery is at 14.5 when idling, mmmmm..., well it could be that the battery has a shorting cell that only presents itself when under load and does not recover until a higher charging current is applied.  Take the battery to a shop for a complete test.  Good luck,

[TwoTired]

Do you still have the stock Vreg?  Do you have another to swap it out?

It may be that the contact points inside may have carboned up preventing contact.  Alternately, they might be sticking, too, preventing release and causing the 14.5 V overcharge at idle because your lighting is off.

Check the voltage at the Vreg black wire and the white wire to see if voltage levels follow your problem description.

I'm guessing but the "vreg" may not be turning the alternator back on properly when the battery voltage falls during idle.  This puts the full load of the bike's electricals solely on the battery during idle dragging volts down.  The Vreg *should*  should turn the alternator field back on during idle so it at least provides some of the power the bike needs.  It's not enough to charge the battery.  But, it does provide some power to lessen the battery drain.

You could check the alternator Field coil Resistance, too.  S/B 6.8 or 7 ohms -ish.

A good fully charged battery normalized overnight will read about 12.6V.  If it has just been peak charged, it will read 13.2.  This is because chemicals in the battery develop a surcharge during the charge process that bleeds off given some time.

If the Vreg checks out and it's wiring, I guess I'd eyeball those coils.  They sound pretty sensitive to voltage levels.  More-so than the stock ones, it seems.  But, I have no direct experience with the Dyna coils.

What spark gap are you using and are the plugs clean?

Cheers,