Hello, new to the forums. I’m Aaron I have a 99 f4. Got it off Facebook marketplace in rough shape, I have done very little to the engine and wiring. I have replaced the battery with an agm replacement, I have replaced a relay and put in a headlight. Very simple fixes I did months ago. Last night…

my bike got a stench off eggs, the battery was hot and swollen, okay so my voltage regulator is bad… as I made my way home the bike suddenly started jolting and lost engine power, I could bump start the bike for a split second, but it would die immediately.

now… when I have a good battery on it, the headlight comes on and off with the kill switch, something it should not and never has done. And the instrument panel is illuminated wether or not the key is on or off,

getting a new battery today and a regulator/rectifier this weekend to solve that issue, if anyone knows of any other issues that cause these symptoms I would appreciate it, Hoping it’s only those things but I’m not sure.

 

Hi and welcome! Unfortunately, you inherited issues caused by previous owner. It worked perfectly fine when leaving showroom-floor and will again once wiring has been restored to 100% factory configuration.

Don't replace perfectly-working parts with brand-new perfectly-working parts. Nothing will change and symptoms will persist. Problem hasn't been positively identified through testing and measuring to arrive at numbers that you can compare with standards in manual. Previous RR was most likely fine, did you test it to verify it was bad?

You have wiring-short somewhere. That's why your dash turns on by itself without key. This short may very well fry your new battery just like previous one.

MAIN GOAL IS TO FIND WIRING FAULT AND FIX IT BEFORE INSTALLING NEW BATTERY & RR

1. connect old battery + charger so you can troubleshoot wiring
2. pull out wiring-diagram and trace ALL wires starting from battery.
3. trace wiring out of battery+ terminal to ignition switch. Measure voltage at each junction. Volts = ???
4. trace wiring into and out of ignition-switch. Measure voltage at each junction, key OFF volts = ??? key ON volts = ???
5. trace wiring to fusebox. Measure voltage at each fuse inlet, key OFF volts = ??? key ON volts = ???
6. trace wiring to fusebox. Measure voltage at each fuse outlet, key OFF volts = ??? key ON volts = ???
7. trace wiring out of fusebox on each circuit. key OFF, volts = ??? Which circuit has power with key OFF???

Somewhere, there will be voltage when there shouldn't be. Need to examine that circuit more closely and restore to factory condition.

WHAT ELECTRICAL MODS ARE THERE ON THIS BIKE???
REVERT ANYTHING THAT'S BEEN MODIFIED BACK to 100% STOCK OEM CONFIGURATION AND YOUR PROBLEM WILL GO AWAY.
There's absolutely zero, zilch, nada no reasons whatsoever to modify factory wiring. It works perfectly 100% when leaving factory and showroom floor. Modifying factory wiring will always lead to mysterious problems like this that'll rob you of money and riding time. Don't modify factory wiring.

At this point, if you don't want to troubleshoot, test and measure, you can just buy brand-new OEM harness from authorised Honda dealer and swap it in. Problem fixed! But it MUST be brand-new OEM harness from authorised Honda dealer. If you guy used harness off fleabay or breakers, it must be tested and measured to confirm it's 100% functional and matches factory wiring-diagram before using. For that effort, you might as well test and measure existing harness on bike and fix it.


BTW - if you want to ADD functionality, like fog-lights or heated-grips, you ADD circuitry with new wiring and fuses directly connected to battery. But you LEAVE FACTORY WIRING ALONE.

 

Thanks for the response, I ordered the parts to have on hand, they are my best guesses atm, I have to go to my shop to grab my power probe and grab a good battery to test off of, the bike has a whole aftermarket tail light assy, I checked wiring for this a few months ago when I installed the battery. Don’t think my issue is there, the power probe will help me track this down however, I wonder if this may be a stuck relay. I’ll post updates on what I find tonight.

I read into the sticky for RR aftermarket options, given my issue is in the RR I will probably order a gsxr unit.

 

Here, let me help you down off that box...

 

Is bike CA model or 49-state? Wiring diagram is slightly different.

Although they are identical between battery to ignition-switch to fusefox. Basically general theme is this:

1. YES, power exists between battery +positive to starter-soleniod fuse to ignition switch.
2. key OFF, NO power leaves ignition-switch to fuse-box or anything else
3. key ON, YES power from ignition-switch to fuse-box

Basically if you measure power on any circuit downstream from ignition-switch with key OFF, that's where problem lies. Trace that circuit and restore to factory condition.

 

Also please draw diagram of how you have this relay and headlight connected.
Was bike just missing headlight and relay, so you re-installed factory relay and headlight?
Or did you have to install additional wiring?

 

my apologies, both were stock plug and play replacements with an oem relay and an aftermarket h4 plug and play led headlight


I did get a good battery and my power probe… next is to test what voltage is coming from the reg over the rpm range and verify the battery is not being overcharged

 

Okay got a new battery and got my power probe hooked up and started probing wires, up to 17 bolts at 6k, RR is on the way, however I suppose I’ll be looking into swapping to the better models RR as the sticky on this forum advises. Glad this was a simple diagnosis, sure had me scared last night. Also getting a new negative battery cable as mine is a little loose at the terminal side where the wire is crimped.

 

I recommend modern series-circuit RR. Old shunt-circuit regulators run stator at 100% output and splits off just enough to power electronics and dumps rest to ground. This heats up RR and stator tremendously and melts insulation off windings (not to mention robs power and hurts MPG).

Very common problem on Ducatis and Aprilias with same solution

Best to upgrade your RR to latest series-circuit with SH-847 regulator. It only draws as much current from stator as needed by bike's electronics rather than driving it at 100% like old shunt-circuit regulators. Startor runs so much cooler and doesn't short out. RR itself is also much cooler and you can touch it after a ride!!!

Get SH847 here http://www.roadstercycle.com/Roadste...egulators.htm/ - don't buy wiring kit with auto-reset circuit breaker

Wiring-connectors here: https://www.easternbeaver.com/Main/E...onnectors.html


Some discussions:

http://v4musclebike.com/forums/showthread.php?t=25778 <-- actual current measurements
https://www.cbrxx.com/threads/actual...s-sh847.49533/ <-- actual current measurements
https://www.douglasvanbossuyt.com/ca...es/motorcycle/ - more temp tests
https://www.cbrxx.com/threads/sh847-...install.42754/
https://www.kawasakiversys.com/threa...o-2017.222367/
https://www.vstrom.info/Smf/index.php?topic=20426.0
https://www.vfrdiscussion.com/index....ed-helpadvice/
https://www.accessnorton.com/NortonC...m.28810/page-3
https://www.apriliaforum.com/forums/...=1#post2845062
https://www.triumphrat.net/threads/c...pgrade.104504/
https://www.thumpertalk.com/forums/t...tator-trouble/
https://www.createfixshare.com/artic...ifier-upgrade/

Good video explaining differences:

 

Not so simple. You've still got 2 wiring faults, at least:

1. headlight circuit not connected properly, turns on & off with kill-switch. Should actually be connected to START button. When START button is pressed, headlights momentarily turns OFF.

2. short in power to dash. Stays on no matter what.