Electrical problem: My bike won't start.

Ok, I've been doing a few chores on my bike before it's MOT (I put the wheels back on, removed the bungee holding the back end together and secured it with bolts/c clips etc).

I thought I'd quickly start the bike up, and when turning on the ignition and hitting the starter button the dash lights went out. Turned it all the way off then on again, and tried again, the same thing happened the lights went out (accompanied by a small sort of click). The dash lights then stayed out.

I then checked the fuses under the seat, and the main fuse behind the side panels, all ok. I then loosened the rear bodywork (on the side that had been wobbling) to check for loose connections, wires to the rectifier/regulator thing and all appeared fine there. So I tried again, the dash lights came on and then went out when I hit the starter button. They are now still out.

Does anybody have an idea what is causing this? I don't think it's a dud battery as it hasn't had any problems turning the motor over recently. I also bypassed the clutch switch just to make sure this wasn't causing issues.

Any help/ideas/suggestions welcome, as I'm meant to be droppiong it off for it's MOT on Tuesday and time is now ticking....

[yorkie_chris]

Well no lights at all suggest its now blown the main fuse (the click)

If I were you I'd suspect that the tray being loose has allowed wires to chafe. That and a general check over connections before starting to look at it any more in depth.

The main fuse is still fine (there have been multiple "clicks") and I've checked for chaffing, I'll have another check though.

[yorkie_chris]

Battery voltage, it's definately worth checking it for charge to rule that out.

Went and checked the main fuse and ignition fuse again, both were fine.

Tried the key in the ignition, dash lights came on, hit the starter, the engine turned and started.

Not sure what thye problem was/is,but I reckon it could be a loose connection, or wire earthing out somewhere....

It's great it's working, but annoying that I still don't know the root cause of the problem.

On another note the clutch switch seems to be working fine now too after I took that off and gave it a fiddle.

Cheers for the help Chris.

[Sid Squid]

If when you press the starter button all the electrics disappear, the problem will very often be a loose battery connection.
What happens is that the small contact area of a loose connection is unable to take the large current needed for the starter and acts like a fuse, the resulting burning being quite resistive.

Ahh so undoing and doing up the battery terminals whilst checking fuses may have helped.

[Sid Squid]

Won't have done any harm.

[yorkie_chris]

Oh oracle of spannering... what do you use on battery connections and other electrics to keep them corrosion free, full of conductive sweetness?

[embee]

There is a special grease for battery terminals (called "battery terminal grease", cryptic eh?) like this

The next best thing, and what I always use, is Vaseline. It works just fine.

You'll find normal bearing type grease doesn't like the acid/moisture.