HELP ! Burning electrical smell - any ideas?

[gixersix]

Hi, just had three days away on the bike including the Lytham to Whitby coast-to-coast run.
On Sunday night, bikes were left out on a hotel car park, and there was a lot of condensation overnight.
This is the first time the bike has not been garaged at night!
Upon first starting, the motor did not catch straight away, in fact it seemed to struggle and even stop, and a cloud of smoke emerged from the right hand side panel of the bike (although the bike was on side stand and of course, smoke rises.....)
The smoke smelt like something electrical was burning, like a burnt out motor.
I stopped the bike, whipped the seat up but we couldn't see where the smoke had come from.
Everything electrical still seems to be working and the bike starts normally now, but shortly after riding away, I still catch the odd whiff of electrical burning every time.
I've not yet had time to start removing the tank and panels yet, to get a closer look, but I have trips away to the TT and Nurburgring coming up, and i'm absolutely petrified that the bike will break down abroad (yes, I AM looking into Euro-recovery).
Does anyone have any ideas where to start looking? Thanks in advance.

[b1k3rdude]

Someone may have had this happen to them so will be able to offer more specific advice, in the mean time pop the seat, tank and side panels off and check all the electrical items, wires & connectors.

One possible answer thats possible but very rare, is that you might have a wire that's chaffed through and its shorted momentarily. It would have then over heated and generated the smell etc.

[Andy FZS]

I've known wet dust to smell as it dries. On the rare occasion that I've washed my bike instead of just polishing it I've sometimes noticed a smell as it dries.

[characticus]

Sounds like the first time this happened you were cranking with the starter motor for a bit longer than usual. This may have allowed a slightly loose connection to overheat in the starter circuit causing the starter motor to slow/stop. Check all of the high current connection (the thick wires) from the battery through the starter solenoid through to the starter. Check cable from the battery negative terminal through to where it bonds to the engine (I'm not at the bike right now and I can't remember where its bonded to to). Make sure all the terminals battery/solenoid are clean and tight. Make sure the terminals crimped onto these thick wires are not loose and look for signs of overheating where they are crimped to the cables. Odds on if there is a problem its in the high current starter circuit.

[b1k3rdude]

What Chara said is very good, I had the battery earth strap on my bandit corrode and it did exactly what he/she described.

[gixersix]

Had a bit of time to think about this - Going to investigate this afternoon - the first thing I'm going to look at is whether the EXUP valve is working, cos I've not stripped it since getting the bike 18 months ago - where is the EXUP motor located?

[allanmac]

Under the tank. If you look in from the front you can just see the pulley on the motor. I would look at the starter solenoid etc as was mentioned earlier if it was the exup motor not being able to turn it would normally throw up an error on the tacho. Had similar happen on a cbr600 and it was the connector for the starter solenoid that was at fault.


Cheers Allan

[gixersix]

Haven't I read somewhere that the EXUP servo-motor is protected from burning out, in the event of the EXUP valve seizing?


I removed the shield cover from the EXUP valve to watch it working, and it doesn't seem to be opening/closing in synch with the revs. There seems to be a bit of a delay between revving and the valve moving, plus the valve doesn't always return to the "at rest" position. I ain't disconnected the cables yet, but they seem free, and with ignition off, I seem to be able to turn the valve slightly by hand.
So I guess I've gotta clean the valve first before anything.
AS I said above, this is first time bikes been left out and everything under the seat seems tight and is corrosion free.


I'll check out the starter solenoid as suggested, but what are the symptoms of a knackered EXUP-servo motor?

[old son]

Are you sure the bike didn't 'pop' back due to unburnt fuel? I've had this a few times, it is quite scary the first time it happens. Bit of a poooof then smoke and an acrid smell. It doesn't happen too often, fortunately!

[Falcon 269]

A knackered servo motor simply doesn't work.  The lag effects you're describing from your observation of the valve in operation sound normal.

Have a look in the airbox and see how much oil is the in bottom.  The crankcase breather vents into the airbox and what you might be smelling is burnt oil not frying electrics.  The latter tend to be terminal, usually the result of a short which will pop a fuse or burn out the wire/connection in question quite rapidly.

PS.  What Old Son said also makes good sense.  If the motor is running fine now, there's a good chance it's nothing more than a passing quirk of the sort we've each suggested.