Beloved BM

decided self-immolation (that does involve fire doesn't it?)
would be a good idea this morning with smoke pouring from
under the tank.
I deprived it of the necessary current and it quietened down.

Tank off to see what's upsetting the thing and I discover
that fat bastard of a cable from battery to inside somewhere
very awkward to get at, has shorted itself against the frame.

What colateral damage can I expect here? and will it be a
bastard to fix?

 

If the short occured from the main positive battery cable to
the frame, before it reaches the starter relay and main fuse,
I wouldn't expect anything other than the cable to be damaged.

If you're cheap and don't want to replace the cable, you could
get by with simply wrapping it up with electrical tape, and
making sure the cable is properly routed so it won't wear
through the insulation again.

 

That sounds promising, thanks

 

If it has been caused by simple mechanical abrasion, then other than the
cable itself, probably none.

Inevitably.

 

I concur with the learned gentlemen.

 

Slip some hosepipe over it?

 

Was the ignition off or on?

Off - Then re route the cable and wrap all of the wires in tape and
you should be OK

ON - Then do the above and then turn on. Most of the time you should
have no problem, if you are really unlucky then;
Diode board
Voltage regulator
and a couple of fuses.(inside headlight)
Timo will be along in a minute with even greater detail, Mr Longhaired
boxhead is the font of all knowledge

This was a common problem with a batch of boxers made at this time,
most dealers should have picked it up by the 5,000 or 10,000 mile
service. They had enough warnings.

Good luck

Boxer Boy
BMW powered for 29 years

 

I had just started the bike and looked at the exhausts to
see where the smoke was coming from.
It then cut out just before I switched it off.

I'm all ears.

 

Sorry, no specific ideas. My first check would be to see if the damage
to the cable looks mechanical (IOW if the insulation has worn
through). The "wrap it in insulating tape" bit would most likely help on
this one. If the magic smoke is still trying to escape after wrapping
the cable then something's drawing a lot more current than it should...

Actually I would replace the cable, mainly because I wouldn't feel
comfortable with one that's shed its insulation - IIRC where it lives,
it does get a lot of heat from the engine which would cause the
insulation to age prematurely.

 

Cheers Timo, there is a friendly boxer man near us and he's
going to see if he has a replacement cable for me.
Fingers crossed.

 

Worth checking the wires to the handlebars where they wrap around the
headstock while you are fixing it all.

 

Said wires appeared to be in good condition.
New heavy cable fitted from battery to solenoid, squirt all
connectors with AFC(?), refit tank.
The clock ticks, good oh. Ignition on, lights show dimly on
the dash but there's no action re the starter.
Not even a little click.
Fuses undamaged.
Would the battery have been damaged/drained by its experience?
Overnight optimate and try again tomorrow.

Thanks all round.

 

Throw a multimeter at the battery to be sure. If the main cable was
welding itself to the frame, you had a lot of current flowing so I'm
not surprised that the battery is feeling a tad weak today.

 

Seems to be waking up already. fingers crossed.

 

Good.

 

Use it as an excuse to buy a nice Hawker Odyssey battery.

Of course if you short that fucker out it might weld the bike to the
planet.

 

Like it!

However it might not be necessary, the bike is back to life
again.
Phew.