burnt out wire

I went to start the bike the other day and it barely turned and then made that "I give up" metallic grinding whir of the starter motor not having enough power.

Oh bugger I thought

So off to get the multi-meter I measured the battery was down significantly and so as I ride it regularly about 60km of highway riding every few days I immediately thought "oh no, the charging system"

This wouldn't be the first time I've had problems with a charging system on a T-Max (see the thread that starts here).

I put the battery on charge and waited about half an hour, I made use of the time and (naturally assuming the worst (its got 120,000km on the odo right)) and started pulling all the tupperware off the bike to expose everything I needed to test, which is:

• charging voltage with engine running (fail, so continue)
• resistance of all the coils in the white wires (I measure over on the left hand side where they emerge directly from the stator) passed
• the possibility of short to ground (alternater death which occured last time)  passed
• test diodes in rectifier - regulator

it was at this point I saw the culprit: one of the wires from the stator (the AC lines) was charred at the connection to the plug and pulling the plug I could see it had tried to melt its way to "freedom"

but looking from the front there was no obvious corrosion on the spade connector...

nor on any of the spade terminals in the regulator connection.  

Happily I found this sooner than later or it would have been worse. Already it had started to melt the plastic of the regulator where it connects to the spade terminal.

So the cause remains a little bit of a mystery and its either a coincidence or was related to a test I did some weeks back in assisting another fellow to diagnose a problem with his charging.

(for those on mobile click this url: https://www.youtube.com/watch?v=4urtqYopbLk)

Now as I said, this could be a coincidence because I'm a bit at a loss as to why doing this would cause a problem with the alternator inlet wires to the regulator. Because after the engine is running the alternator (via the regulator) has to power all the accessories of the engine anyway (or the battery will go flat right?), so there would be no more or less demand on those wires carrying power from the alternator to the regulator.

If there was any power spike it would be very short and I'd have thought that the ECU or other electronic parts of the dash (fuck, the whole dash is electronic) would have been screwed before a copper wired designed to take high loads would fry ...

Anyway its weird that it happened and I conclude that I must insert this bit.

Back to the repair

In the above shot of the plug you can see there is a small locking plastic tab (in the unoccupied hole) that is designed to allow you to insert and remove a spade connector ... sadly that was melted (think hot melt glue) to my connector and I had to get "violent" on it to get it out.

you can see there is a little raised bit at the back which would also act to prevent it falling back out ...

you can see that the wire shows discoloration on the copper (and a dent in the plastic where heat has assisted the insulation into melting close to the other conductors) and so I suspect this is all a coincidence and what has happened is the result of

1. age working against the connection between the crimped spade connector and the copper, resulting in resistance buildup
2. resistance build up generates heat
3. heat changes the wire to a greater resistance
4. repeat as a cycle from #2 until thermal runaway causes connector death

So when I re-crimped a new spade connector on I also soldered it (and to my American readers that's got an L in it ... so its not soddered its sold-er-d like when you sell something its sold not sod)

Also worth noting is that despite inspecting a number of spade connectors, while they were all a perfect fit for the spade terminal, they were all a fraction of a mm too wide to fit into that (probably only Yamaha) connector ... so further destruction was warranted to get the bloody thing in...

which is it as shown above. I simply trimmed that one wire, but if future surgery is warranted then I'll have to revise how that plug is going to look. For a start its (to me) important that the wires don't just fall out from vibration, and so the multiple levels of locking plastic connections are important. Now I have one wire which doesn't have that.

so here it is all trimmed an dput back (not shown is that I've added a cable tie just to the left to hold that cable run against the other, hopefully that will prevent any pull on the spade connector (as well as its internal friction ...).

All going well now and behaving as expected ... I'll have another look at it when I do my next belt service whereupon that side cover needs to come off and I'll have ready access to have a peek.

So, all in all about 5 hours work (including a break for a coffee and custard tart (which I'd picked up cheap the day before when I'd made my last 60km run into town before this debarcle)

So there you go ... like the old saying says and engineer can fix for a dollar what can be replaced for hundreds.

This is also why I don't mind owning an older bike, which is simple enough that I can fix because if I'd taken it to a dealer it'd be hundreds (and man, if you see what Yamaha did to the model after this its a technicians nightmare ... almost making certain that they are scrapped when a tiny thing like this halts them).