Bought a voltmeter for my GS and am wondering what's the best/simplest way to wire it up. The one on my VFR is straight off the battery with an on/off switch but it's a bit of a PITA so I would rather have it on permanently, either on the ignition or the park light circuit (I can turn my headlights on or off, don't know if US models are the same). One thing that I'm wondering about, If its on the lighting circuit will I not get a slightly false reading? Thanks.

I would say either the battery, or splice into the regulator wires. As far as I know, those are the two biggest things to monitor. There's not much left, unless you want to monitor one particular circuit. That being said, I do believe the headlight circuit would give a false reading as to the overall voltage of the machine.

Take a look at [THIS PAGE] to see how I handled a similar device.

It sounds like you won't need the "quick connect" idea, but the ignition-switched connections inside the headlight bucket might help.  (Photos are of a '96 model.)

Thanks guys, I will have a look at that.

I would do (+) to the battery and the other to ground

Kerry, I found the brown and grey wires in the headlight enclosure but they were hooked up to my park light. Nonetheless I wired the voltmeter into them but the reading was way off. So I went the (kind-of) direct route. Being an ex police bike mine has got a plug under the seat which comes straight off the battery, so I just plugged into that. Found a mini toggle switch from my guitar stuff and wired it in. Just have to find a way to waterproof the switch as that could give trouble in the future

Cool job! 

.... Just thinking though ... Wouldn't a ammeter be more useful for bikes? .... Show you if the thing is charging at any point or if its ok .... And how much 'flow' is going to the battery depending on its state of charge
Voltmeter shows how much energy in the circuit ... But not if your battery needs volts or attention ... You can have 14.5 showing while its running and the battery still be dying I think? .. Still handy for when you first go to start the bike .... But if the battery is already too low it's too late?

I don't know much about electronics, but I think you have a point. I do remember the battery on my VFR was empty once, it showed 12 volts but when you tried to start it, it dropped to about 4 volts! My main reason for fitting voltmeters is to watch for over charging and hopefully catch it before it does any damage.