It’s wet. It’s dark. It’s very, very cold and I’m about halfway through a 90-mile journey home from Bath to Slough one December night. My heated grips are cranked up to max, and so is the heated vest, and I’m still cold. But it’s ok – the Bandit’s just had its oil change, and I even put fresh brakes on and topped up the ACF-50 coating. It’s less than three years old, and it’s Japanese – bulletproof, right?

Wrong. Or so it seemed.

At first I thought it was a trick of the light, a reflection of some passing car – the digital speedo jumped 10mph for a fraction of a second and then was back to normal. But I know computers – and glitches like that are never just a one-off. Sure enough, a minute or so later, it happened again. Then it began jumping to lower speeds, and staying there for longer each time, reading more and more erratically until I had to use my tachometer and GPS to know that I was still at my usual cruising speed (75-indicated). Not good.

Already my diagnostic mind was considering possibilities. The only thing that had changed recently was the addition of the heated jacket. I’d wired it directly into the battery posts, along with all my other electrical modifications. There was so much attached that I had to replace the standard phillips screws with longer bolts, and I began to worry that I’d finally done what I’d always been warned against – fitting too many electrical gadgets and overloading the charging system. And I already knew how much things like ECUs cost to replace. Definitely not good.

I slowed down and stopped on the hard shoulder. I wanted to see if shutting the bike off and back on again made any difference – after all, it works for normal computers, why not for an ECU? But once back at cruising speed the issues came back with a vengeance. It would flip wildly between 30 and 60 miles per hour and everything in between. I wondered about water getting into the speedometer sensor down on the sprocket cover, but if so why had it never happened before? I’d definitely ridden in worse rain.

Then the problem got worse.

The gear selector decided it was no longer sure which gear I was in. At first it dropped a gear, then flipped to first, then zero, then gave up entirely and displayed the “CHEC” letters over the odometer. It was completely confused, and might as well have displayed “HELP!”. As soon as the next service station popped up I slowed down, only to discover that the Neutral light was lighting up as well. It’s amazing how used you get to using the gear indicator, until all of a sudden you don’t have it…

I stopped under the shelter of a petrol station and experimented as best I could. I disconnected my vest and switched that over to its own Li-Ion battery. I turned off the heated grips and popped the GPS from its mount. None of it made any difference – and now the ABS light and neutral light would flicker as the engine rev’d up – it was like being back on my old 6-volt 70’s Honda. But the engine ran, and the lights were OK, and with nothing obviously loose and no tools I decided to press on home rather than call out the RAC. After all, it was either an Italian-style electrical gremlin or I’d cooked the charging system through my judicious use of mods, neither of which a man in a van was going to be able to solve that night.

I made it home and despondently went to bed. When I got up the next morning and rode to work the speedo was back (yay!) and so was the gear indicator (woo!), but the neutral and ABS lights were still dancing in time to the engine and I almost had a heart attack when I slipped into neutral at a traffic light and the Oil Pressure warning light lit up.

The rule is that you kill the engine as soon as you see that and you might be able to salvage what’s left of your crankshaft and valves, but the neat way that the light had come on exactly as the neutral light lit up, and with no change in engine note, made me cautiously drop it back into first. And sure enough, as the neutral light went out, so did the oil pressure warning. Great, I thought – another electrical problem. But at least my engine was OK.

Once at work I pulled down a high-res PDF of the GSX650F service manual (good luck finding a Bandit one, but they’re mostly the same bike) and spent my breaks poring over a giant A3 printout with a highlighter trying to find a logical place where a break in the wire or bad earth could cause the peculiar symptoms I’d experienced. In the end the only common denominator was the dash – an extremely expensive self-contained computer and LCD unit that I really didn’t want to have to replace.

That evening I spent three hours tearing my electrical system down and checking every plug I could find. I tore the dash out – nothing. I tore the battery box out until I could check every relay and – good news – I now know where the ABS pump is located (hooray!). I had no multi-meter, and the only tools at my disposal were the Suzuki set, my Leatherman, and a funky Draper multi-socket hand-driver I’d received in the mail for renewing my Ride subscription. Everything else was in storage. Fun times.

The good news? I figured it out. Eventually. I’d been so focused on bad grounds or my own inept wiring that I’d forgotten about the bits that the dealer had fitted before I’d even bought the bike. I remember the dealer telling me what a great value-add it was that their workshop fitted Optimate charing connectors to every bike sold. I remember being really pleased, and made a mental note to buy an optimate charger at some point in the future. What I don’t remember is him warning me that the waterproof plug they fitted was really good at keeping water in once it had worked its way into the rubber plug and corroded the crap out of it.

So yeah – let’s just say I don’t have an Optimate charging lead anymore, and I didn’t blow up my own bike.

On the plus side, some further research confirmed that the alternator on the 650s outputs a solid 400W – probably an up-rated unit designed for the 1250, and that my accessories together with the running draw of engine, lights etc. meant that I could’ve added a heck of a lot more and still had juice to spare. And once I was able to put my multimeter into play I discovered that unlike every other bike I’ve ever owned that required 4000RPM to spin the alternator into actually producing enough current to charge the battery, the Bandit’s industrial-strength, military-spec unit actually supplies a solid 14V at idle. Badass.

So yeah. One crappy, low voltage short, and the dash goes crazy. I’m definitely getting myself an on-board voltmeter…

…and a proper damn garage. With all my tools.