My ST1100 randomly almost caught fire

I bought my ST1100 at least partially because it is supposed to be a reliable bike. Here's my story.

I live in the Bay Area of California. I bought a 1997 ST1100 from a guy who took great care of it. A solid, sober, veteran of the Navy. My bike has 44,000 miles and I've owned it for most of a year. I've ridden it without issue and serviced it.

Two days ago, I was fully suited up in my riding gear -- ready to go for a ride. I removed the cover. (This week, i was living dangerously, leaving my bike in the driveway with a good cover, instead of inside the garage).

With the key in hand (i.e., with no electrical device on), I set the cover down and approached the bike to sit on it.

Instantly, a cloud of smoke started coming out from the bike!

I had ridden this very bike from San Jose to San Francisco on a road called Skyline Boulevard -- a beautiful drive, only a few days before and without any issue whatsoever.

The smoke became so thick I was sure a fire was about to happen. I'm in full leather with helmet and gloves on and it's 85 degrees (F) and I am stunned and incredulous that this well maintained bike is violently smoking without being touched except to remove the bike cover. The smoke got worse. The bike was RIGHT next to a boat (which has a 50 gallon full fuel tank) and I instantly began to think, "this damn bike is going to catch fire and go up next to the boat!" ...and the boat was next to the house.

The smoke became so acrid I couldn't inhale it. So, in full gear, I ran into the house, grabbed a charcoal respirator and a fire extinguisher, run back out and the bike was still smoking, but the cloud was beginning to thin out.

It stopped.

The aftermath: I have no idea (days later) why this occurred. I removed the seat and found a harness that was completely disintegrated. I mean: Gone.

I moved the bike to the street, where it sits to this day. I moved it there because I don't want a fire hazard near my house.

I could post pictures of my bike. It is the cleanest 97 ST1100 you would ever see.

But, it's scared the hell out of me. I spoke to two mechanics who are puzzled.

I have only one thread of a theory. Months ago, I had a respected shop work on the clutch on the bike. The clutch was not releasing. They replaced the stock headlight with an "H4" bulb. I Googled it, and that bulb consume much more current. Could that have melted wires?

That is a theory, and a weak one because the bike burned itself up and I had not even put the key in the ignition!

I'm having it taken to the same mechanic tomorrow, but I must say, keeping that bike in my garage or near anything that is flammable scares me.

I'm really torn up about this. It may cost a fortune to repair it. Is this a known ST1100 fault?

My bike, at the races in Sonoma, California. Her name is Ashley.

Ashley tried to burn down my boat.

And failed.

My first guess would be that a :sm1: chewed up your wires and it caused a short.
What area on the bike was the smoke coming from?

The stock bulbs (there are two in there) are 45/45W. These draw 7.5 amps. The headlight fuse is rated at 10 amps. Changing the stock bulbs to H4 means something of a higher wattage was used. Do you know what they installed?

If they went with the usual 55/60W H4 bulbs, this results in a draw of 9.17 amps. Even at high beam, the draw comes to 10 amps, so that is the maximum the circuit is designed for. If the dealer installed anything higher in wattage, that may have resulted in some melting of insulation, if the fuse didn't blow.

Since the harness had a definite short somewhere to cause it to fry, I'd be looking to see if the source is at the fuse panel and which fuse, if it isn't all too severely damaged.


EDIT: Just saw Igofar's post and . . . stored outside, under cover . . . yeah, that sounds very likely and the little critter may have been in the middle of a snack just as you pulled the cover, making him disturb his lunch and causing wires to arc. Look for a fried mouse too.

Ashley971 said:

I moved the bike to the street, where it sits to this day. I moved it there because I don't want a fire hazard near my house.

Click to expand...

You could have just removed the battery. You had an electrical meltdown. There was a short in your wiring harness. No battery no short no acrid (always a clue to wire insulation burning) smoke.

It's interesting about the new bulb. If it's not the Honda spec 45/45 bulb then it needs to be modified to fit your bike. This means cutting off the two bottom tabs. But the unlike the ST1300 the 1100 needs all three tabs to sit in the headlight properly. To do that it needs aftermarket shims (the 1300 doesn't need the) to properly support the bulb. So I wonder if they installed the shims. While it might be possible if sitting cockeyed in the socket the bulb/wiring might be at risk it seems a stretch.

I'd suspect a chafed or chewed wire. Odd that it happened when and how it did. I'd almost suspect a static spark from pulling the cover off with fuel vapors accumulating under the cover. But that would really be a stretch.

It's a good guess but not a certainty that the problem occurred within the charred area or your harness.

Hope you track down the cause. Remove the battery. And replace or get your fire extinguisher refilled.

There are several possiblities. Larry's is the most possible. You did not say what harness was fried, nor did you mention if any modifications to the electrical system (aka - owner's farkles) had been made. Since you did not touch the bike when the melt down began, either a critter gnawed through the insulation or the clock circuit (are there any other 'always on' circuits on the 1100?) had damage to the insulation that shorted at the moment when you pulled the over off. My problem with this scenario is all of the circuits are fused - and if you short a wire to the frame, only the fuse blows - no fire, no smoke, no drama.

The exception to a fuse blowing with no real damage could be an improperly installed addition to the wiring harness (aforementioned farkle) - such as an unfused powerlet or unfused circuit to power heated clothing.

Pull the battery to make the bike safe and find another ST owner in your area. I doubt this is going to cost a fortune to repair - unless of course, you take it to a BMW shop for the repair (see recent BMW oil change thread....).

P.S. I hope you did not use your fire extinguisher. Dry chemical powder is extremely corrosive to aluminum and can cause more damage than the fire. Sure is a pretty bike - hope you can get back to riding soon.

That mouse emoji made me laugh so hard! Best laugh in a while.

One of the mechanics thought that it could be a mouse. That's about as good of a guess as I've heard. Problem there is the cover is very tight, we have no mice in my area, and we have 4 well paid cats that patrol the area. (There can not be a cat emoji as great as that mouse emoji, by the way. I won't even try to find one.)

Here's a picture of the bike taken minutes ago. You can see the remains of the harness between the left frame rail and outer plastic cover.

I agree with SMSW & IGoFar. A mouse might have chewed through the wires or maybe there was a botched farkle installed. Is there a battery tender charging lead (SAE connector) wired to the battery? If so, maybe you accidently pulled on that hot wire when you took the cover off? I can't be the H4 bulbs because there is no power to that circuit when the bike is off. Good luck getting it back together!

Thanks, Good People, for the replies. If I bought a brand spanking new bike, the advice of a dealer service advisor wouldn't be as helpful and supportive as yours.

I omitted a few minor items in my original post. I was on my way to an off-site meeting the morning of the "fire." And any delay would make me late. New job, with boss attending (and his boss). Interestingly, I grabbed my backup bike to make the meeting and the battery was dead. Good times. Anyway, I didn't have time to do investigation or remove the battery. I just returned last night.

There were no farkles or modifications to the bike electrical system.

I'm going to find out what the wattage of the bulb was. On my receipt, it only states "H4." And, if it was at or near the fuse current limit, maybe it could have compromised a wire insulation integrity without blowing the fuse (?).

More than anything, I was asking to see if the ST1100 community had ever heard of such a thing. I certainly have not.

Also, I am advised by two mechanics that replacing the harness will be (here's the range): 5-8 hours of labor. A new harness is $700. One mechanic wondered if something called a CDI box was damaged, and if so, that box replacement is over $1000.

To be positive about it, I think about what would have happened if i was riding the bike in a bad traffic environment when this happened.

This is a firST; in my 18+ years on the forums. My bet is on a botched electrical farkle. Or the mouse conjecture.

My guess is this is DIY fixable. Please remove the left Side Cover and take a picture that actually shows the area so we can help diagnose the cause/damage. TIA

In a way you were lucky in that the wire sacrificed itself to end the crisis and stop further damage. Replace (splice in new) the individual wires' damaged sections may be all that you need to effect a repair.

John

Ashley is on the way to the shop. I'm not even at home now. I will definitely post findings as to what caused this. If this is some long term reliability/safety hazard for the ST1100 maybe this will help the next owner of an ST1100. Replacing the harness means nothing if the cause is not found -- because it could happen again on this bike.

One other thing strikes me: that harness is located too close to the seat latch. It's a bad design, it seems. If (and I do mean if, because I doubt that it applies) if the harness somehow became sandwiched under the latch, that could cause insulation tearing. But, that's grabbing at straws. Nothing comes close to making sense except that higher wattage bulb.

TruST me, the bulb had nothing to do with this. And this is no design flaw in the ST1100. As I said, not in 18 years has something remotely like this happened. This is human error (or animal interference) at some point, plain and simple. There is a cause but it isn't Mother Honda. Somebody or something messed with your ST that eventually resulted in a dead short on an apparently unfused circuit, the melted wire becoming the last ditch 'fuse.'

In any case, I'd highly recommend a second opinion of whatever your shop tells you, preferably an experienced ST1100 rider/DIYer.

Oh yeah... "too close to the seat latch"...(?) The seat latch is at the rear of the saddle, not near the spot in the picture.

FWIW

Edit: After looking closely at your picture, something struck me as odd so I checked my ST and there's no OEM wiring there. The loom runs well below the frame rail.

John

John OoSTerhuis said:

Edit: After looking closely at your picture, something struck me as odd so I checked my ST and there's no OEM wiring there. The loom runs well below the frame rail.

Click to expand...

I haven't had a chance to look at my ST1100 but I don't remember any wiring loom running in that area either. Looks like you've had some modifications by someone.

Looking at the pictures, added wires may have rubbed against the sharp edge of the gas tank and eventually shorted out - or a mouse/rodent could have enjoyed a tasty meal. AFAICT, those wires that melted do not appear on any of the three ST1100s that I have.

The headlight is frequently upgraded from the 45/45W to a 55/60W with no ill effects. None. Some have said they've gone to even higher wattage bulbs with no worries. I'm still curious as to how your mechs did this. Look at the bulbs through your headlight to be sure they are seated and aligned correctly. Still it would take some real electrical gymnastics for them to be the cause of your bike's meltdown.

And they may have merely referred to the factory bulb(s) as 'H-4'. Or your bike had already had the bulbs upgraded and the shims in place.

The fact that the damaged loom and/or it's location is unfamiliar to very knowledgeable ST owners with extensive experience is really troubling. Whether it's an add-on or relocated factory bit- being out of place is a clue. And given it's location rubbing against the frame (or is that the gas tank?) and chafing is a real possibility. Somebody seems to have done something non-spec to your bike.

John OoSTerhuis said:

TruST me, the bulb had nothing to do with this. And this is no design flaw in the ST1100. As I said, not in 18 years has something remotely like this happened. This is human error (or animal interference) at some point, plain and simple. There is a cause but it isn't Mother Honda. Somebody or something messed with your ST that eventually resulted in a dead short on an apparently unfused circuit, the melted wire becoming the last ditch 'fuse.'

In any case, I'd highly recommend a second opinion of whatever your shop tells you, preferably an experienced ST1100 rider/DIYer.

Oh yeah... "too close to the seat latch"...(?) The seat latch is at the rear of the saddle, not near the spot in the picture.

FWIW

Edit: After looking closely at your picture, something struck me as odd so I checked my ST and there's no OEM wiring there. The loom runs well below the frame rail.

John

Click to expand...

plus 1 something unfused caused the problem.. Take a wire, put a fuse holder in the middle of it. put one end to the battery + and the other to the - and see how fast that fuse blows.

Honda uses (at least on my 1300) a tubular loom unlike any I've seen in the auto parts stores. If this was the case with the 1100, then you should be able to tell very quickly if the burned harness is OEM or POM (Previous Owner Made). The loom on the 1300 is a thin vinyl tube that looks a lot like flexible heat shrink tubing (before heating and shrinking).

Yup....I'm in concurrence with several: the issue is NOT a design flaw.
Either a critter chewed something causing a short (check for signs of rodent work in the air box area, etc.) OR, more likely judging from the pictures, misrouted wiring that had insulation rubbed through or that was stretched to the point the most of the strands were broken and the remaining (few) wires got hot and smoked.
Have fun!

Thanks all for the insightful responses. Given my time and location constraints, I was in no position to identify the harness, or whether it was OEM or not. Regardless, it's in a bad location. That's why I said it appears to be a bad design. I'm not ruling any of the causes mentioned out. I repeat: it's strange that the bike sat for a few days and went up simply after taking the cover off. This great forum confirmed that this was a rare event.

I wonder if that bike had been set up for heated clothing. No way would Honda run a harness over that frame rail. It may be in close proximity of the seat and when you sit on it you could press down on it more to the point where it would damage the insulation.
Here is a zoomed in photo of an ST1100 that shows there should be NO harness running over the top of that frame rail. Some amateur screwed the pooch on that bike and should be given a stern warning not to do that again.