Commando on fire

Thought I should pass along a hard earned Commando lesson in case there is someone else as stupid and careless as I was. My Commando would not start when I got it out of winter storage this year. I have been busy with other "stuff" and I have a running BSA and Ducati, so I had put off finding my problem until yesterday. I took the Commando off the Battery Tender and began troubleshooting the problem. No spark. Battery good. Voltage at coils. Pulled the points cover (I run a Boyer) and I had power there, but I found a bullet connector on the Boyer stator PC board was improperly crimped (by the factory) and it pulled right off the wire. It's been running that way for many years. I replaced the connector and the Commando fired up second kick. Time for the Happy Dance! I rolled it out of the garage and it was happily idling while I geared up for a ride. It suddenly died and I look over to see smoke and fire pouring out from under the seat. Fortunately I got the fire out before it caused too much damage other than many of the ground wires with the insulation burned off. It was still sparking from the now uninsulated wires but I managed to get the battery disconnected before it caught fire again. I was extremely unhappy and just put it in the garage in disgust. All evening I was thinking what could have caused the fire. This morning at about 6 AM I was laying in bed still thinking about it when the answer came to me. The Battery Tender pigtail and the arcane Brit positive ground system were my undoing. A Battery Tender quick connect pigtail is very handy on bikes that don't get ridden every day or two. I have them on all my bikes, but they were designed for negative ground vehicles. When you pull the Tender from the pigtail it leaves one side of the polarized plug exposed. There is a rubber insulating cover you are supposed to snap on the pigtail but I had neglected to do so. This is not a problem on a negative ground bike as the exposed metal part on the pigtail is connected to the negative side of the battery. BIG problem on a positive ground bike if that exposed metal pin touches the bike frame... like happened to mine while it was sitting there idling. When the pin touched the frame the fuse didn't blow but the huge amperage pulled through the wiring harness caused the insulation on that big bunch of red ground wires going to the battery to melt and catch fire. I am fortunate I was close by the bike, not riding at speed and that the current draw dropped the voltage to the Boyer which killed the engine and got my immediate attention. So ALWAYS cover those Battery Tender pigtails when not in use so you don't have the unpleasant experience of seeing your bike on fire. Hopefully I am looking at just a bit of wiring work to get the Commando back on the road... but it certainly could have been much worse.

Thanks for that reminder. I hope you get your bike back together in short order. I remember the pictures of it from your build thread and it is a beauty.

That reminds me...

When we moved back to the UK from Holland in 1998 we rented a flat in Kingston-Upon-Thames. I used to keep Nellie at my local pub, the landlord was a biker, the security good (he had a dog the size of a pony) , and what better place to finish a run.

One afternoon I collected the bike and headed towards home, at a junction a few minutes later a chap waved at me, I waved back, then another so I waved again & pulled away.
At the next junction, another couple of people waved & I waved munificently back - fantastic, the sun is shining, all's well with the world, and it's demonstrable that riding a classic British motorcycle brings joy and happiness to the lives of those you just pass by.

As I stopped at the next junction a chap ran out of his house with a bucket of water, another ran across the road pointing, waving and shouting, what's that, can't quit... oh... fire... fire?...where?

I looked around, then idly down... Holy Crap!!!!!, THERE's THE FIRE & it's between my legs! Ohhhhhhhh so THAT's why people were waving!

The carb must have spat back & caught the big oil dampened sock type air cleaner on the SU then fitted and it had also caught the oil in the airbox alight. I was very lucky & sourced a replacement via BI or NOC-L from Captain Norton & yes, we did get to go for a spin that afternoon.

Whenever my carb spits I pause to make sure that any wisps of smoke are not the start of something requiring the attendance of shiny red vehicles! (& I keep meaning to get an extinguisher in the garage)

Mike

That sucks!

Doesn't the battery tender Jr have auto-correcting polarity? What I mean is, couldn't you reverse the the "+" & "-" on the battery? I could be wrong so don't try this if you don' t know!!!

Thanks for the heads up. From now on I am going to make sure that I put the rubber cover on when I pull mine off the battery tender.

flyboy49,

The exact same thing happened to my Commando two years ago during the rebuild. Battery Tender Jr. pigtail shorted against the Z-Plate and smoked the main harness. I also had forgotten to put the little cap back on the pigtail and when I leaned against it .....it welded itself to the metal plate. My fault and I always think about this when I disconnect the plug from my bike. The Battery Tender Jr. does not have a polarity correcting feature and it must be hooked up with the red terminal to the + post on the battery or it will not charge the batt; which in turn makes the exposed post on the pigtail hot.

I got a replacement main harness from Commando Specialties for around $130.00 and all was well. The new harness has fewer wires because it is for a Commando Roadster. The OEM harness has more wires because it is designed for all models including Police and Interpol units.

Another valuable lesson learned........

when I don't use my commandos I usually pull both fuses out.

I just use the clip leads from the tender. But I also pull the fuse out when not riding. What amp fuse did you have in it? It should have blown with a short like that. I use a 17 amp (US). Glad it didn't ruin anything else than the wiring.

That's not unlike the other week when I went for a ride, I didn't fasten the dzus fastener all the way with the side panel, and of course it came off at 50mph on the road. Had to stop and rescue it. Like you I thought later that I knew I didn't have the fastener connected right, just old age crap, at least for me.

Same thing happened to me. Smoked the wire right up to the battery, but no fire. Now I have a 7.5 amp fuse installed in the negative wire from the pigtail to the battery connection and kept the fuse on the positive side.

When I installed the BT lead, I recognized the potential safety hazard and employed a two prong approach. 1) procedure.. always use the rubber cap. 2) (for when I got distracted or forgot 1) I tie-rapped the lead so close, it can't reach any metal. Kinda same idea as grabbing a snake right behind the head.

Wow, hadn't thought of that scenario. Thanks for posting. Adding an inline fuse would be a good idea & cheap peace of mind!

It should have blown with a short like that

Click to expand...

No. Think about it. The pigtail has a fuse in the positive lead because it is made for a normal negative ground system. The bike's fuse is on the negative side. When the exposed pigtail lead touches the frame, the path is closed from the frame thru the negative lead on the pigtail to the battery and from the positive wires of the bike's harness back to the frame. No fuse in the circuit!!

Ron L said:

It should have blown with a short like that

Click to expand...

No. Think about it. The pigtail has a fuse in the positive lead because it is made for a normal negative ground system. The bike's fuse is on the negative side. When the exposed pigtail lead touches the frame, the path is closed from the frame thru the negative lead on the pigtail to the battery and from the positive wires of the bike's harness back to the frame. No fuse in the circuit!!

Click to expand...

You know what, as a follow up to my previous post and the above, the simplest solution may be to cut out the section of wire in the battery tender pigtail that has the fuse, flip it over and solder back in thereby moving the fuse to the negative wire.....

Thanks for the heads up! I use a tender all the time and just let the end fall when I disconnect it.
Wont be doing that anymore.

Also, just a reminder, unplug the zener to allow complete charging.

Ron L said:

No. Think about it. The pigtail has a fuse in the positive lead because it is made for a normal negative ground system. The bike's fuse is on the negative side. When the exposed pigtail lead touches the frame, the path is closed from the frame thru the negative lead on the pigtail to the battery and from the positive wires of the bike's harness back to the frame. No fuse in the circuit!!

Click to expand...

Got it. Didn't think about that, and that's a reason to fuse everything. There's lots of good equipment that's fused in both lines, most likely just for that reason. You never know where the short is going to happen.

concours said:

When I installed the BT lead, I recognized the potential safety hazard and employed a two prong approach. 1) procedure.. always use the rubber cap. 2) (for when I got distracted or forgot 1) I tie-rapped the lead so close, it can't reach any metal. Kinda same idea as grabbing a snake right behind the head.

Click to expand...

+1 concours... Its very basic and logical stuff.. I cant believe there are sooooo many that have had the same problem :shock: :shock: :shock: :shock:

concours said:

When I installed the BT lead, I recognized the potential safety hazard and employed a two prong approach. 1) procedure.. always use the rubber cap. 2) (for when I got distracted or forgot 1) I tie-rapped the lead so close, it can't reach any metal. Kinda same idea as grabbing a snake right behind the head.

Click to expand...

Why would you use the aftermarket connection when it looks like the factory plug and socket is fitted to your bike?
I don't use a tender but a regular charger every 2 or 3 weeks
I'm not trying to be a smart arse just genuinely curious

Jed

Jed said:

concours said:

When I installed the BT lead, I recognized the potential safety hazard and employed a two prong approach. 1) procedure.. always use the rubber cap. 2) (for when I got distracted or forgot 1) I tie-rapped the lead so close, it can't reach any metal. Kinda same idea as grabbing a snake right behind the head.

Click to expand...

Why would you use the aftermarket connection when it looks like the factory plug and socket is fitted to your bike?
I don't use a tender but a regular charger every 2 or 3 weeks
I'm not trying to be a smart arse just genuinely curious

Jed

Click to expand...

Commonality. If I only had one bike, I'd pay the $35 for a shaver plug, but given the dozens of things here that are used sporatically, Battery Tender plugs are everywhere. Also commonality for accessories (shown)

I actually took a piece of larger heat shrink tubing and put over that plug, so even if I did accidently drop it or whatever it was shielded. And I also plug in the little rubber doohickey to make sure, but the heat shrink condom shield is a good addition as well.