So I got going on the light resto of my paso, cleaned the carb, checked the belts, changed the oil/plugs & fired her up. Well, had to use a jumper box because the only batt I had was a ballistic EVO that was in my husky 630, I had disconnected the headlamp so I would have more cranking power and to not kill the battery. Starts and idles fine but when you give it has it stumbles.

Went and bought a proper new AGM batt for it. Starts fine. Here's the thing, the battery light stays on, and if you honk the horn at idle it dies.

I checked/cleaned the ground near the shock, the one near the reg/rec and the one on the left frame spar (blue wire). Any ideas on why it would just die like that?

The bike has just been sitting in a garage for 8+ yrs, there's no critter damage and it's all complete.....stock except for the exhaust is from a 750 I think.

Put a multimeter across the battery and see what voltage it reads . Ignition off it should read around 12.5 to 13.5 volts. Start it up and let it idle. Battery volts will be less than before as it would have degraded slightly due to the starting current. Slow rev the bike up and by about 3000rpm it should be reading about 14.5volts, but no more than about 14.9volts. If all is good hit the horn button and see what happens.

The battery idiot light on sort of suggests the regulator may be shot, or at least a dodgy earth. The above battery volts will pretty much conform it.

Another thought is the LHS switch gear is knackered or the wiring to it. Unscrew it from the handle bar and see what happens. I haven't looked at the schematic, but the horn switch most likely has 12 volts on it. If when pressed it shorts the 12 volts to the handle bar, it could create enough of a voltage drop to kill the motor. I would have expected this to blow a fuse, but like I said, I haven't had a look at the schematic.

Cheers.

Nick.

I agree with Nick regarding checking the battery for charging.
Regarding the horn killing the ignition, a faulty ignition switch is a possibility. The ignition switches on the Paso series is well known for bad internal contacts.
The horn draws a lot of current so high resistance at the ignition switch contacts means the the voltage drops when the button is pushed. It could be dropping enough for the Digiplex to stop the sparks.
There is a wiring mod in the FAQ to fit a relay to take the load from the switch.

Ok, yeah I'd forgot to mention that I did check the battery while running. No change in voltage when revved. Also there are 3 wires coming out of the magneto, 2 yellow one red. The red wire seems to have some heat damage to the connector. Looking at the schematic that's the charging wire. I discinnected that wire & started the bike, same exact symptoms. (I should add that the horn is working, it's not the switch grounding as the horn blows...until the motor dies). In another attempt to diagnose the issue I disconnected the reg/rec and started the bike. Basically same symptoms, except the battery light was no longer illuminated. Im thinking either the reg/rec or the magneto is shot, or both. There's acid staining on the swingarm indicating there was an overcharging issue at some point. I guess I could disconnect the charging wire from the magneto and check it on the multimeter (AC, right?)......

Well you have confirmed that the battery isn't charging. It needs all 3 wires, the 2 yellow and the red to charge with that regulator. You should check the alternator for AC volts across the 2 yellows when the engine is running. The red wire is a centre tap, you should get a lesser voltages between either of the yellows and the red. If you're getting AC volts at about 15V / 1000 rpm across the 2 yellows the alternator is probably OK. In which case you need a replacement regulator.

The three wires from the Alternator are yellow (2) and red. The two yellows are power output. The red is for the charge (idiot) light. Don't connect the red to an unknown rectifier, it will melt wires and is a 'wrong' connection. A new reg/rec might not have a terminal for the red wire - don't worry it can be left off. The standard Energis rectifier is a truly nasty piece of kit, any replacement is bound to be better. For the lonely, an easy mod will have your charge indicator working again if the reg/rec doesn't have the terminal.

Alright, got to fiddle again for a bit. @5v across the two yellows >1000rpm. So the magneto is toast?

That's weird, because if I put the + lead of my multimeter to the red wire coming out of the magneto, and the - lead to a ground I get 12v DC......

Well there is no way that any of the leads from the alternator are going to produce 12v DC. Unless the regulator is faulty and there is leakage back through it from the battery.

Stator? Lol ok. The red wire goes into the sheath with the two yellows and then into the cover on the left side of the motor, which I have not removed yet. The weird thing about all this is that my uncle told me the bike was running fine the last time he rode it (albeit about a decade ago). The bike has low mileage and is basically 100% stock, in a previous post someone mentioned the ignition having poor connectors? Is this the ignition (key) switch or the right switchgear starter-on/off switch?

I could understand that connectors four corrode but how could a reg/rec or stator toast itself just sitting......bike didn't even have a battery in it for that time.
I looked at the FAQ and breezed through the the schematics for the addition of relays, those look like a good idea, once I get this thing running correctly I'm going to do those mods as well.

Yeah ( Derek ) if the red wire wasn't connected to earth ...... but it is and I reckon if that scr shorted it would take 1/2 a nanosecond for something to blow , if your lucky you might see the flash reflecting off the workshop walls and a mushroom cloud making its way across the ceiling but you'd have to be quick