Where there is smoke...

[RVFRick]

Where there's smoke...

Earlier this afternoon I finished reading Rossi's entertaining autobiography. Since the weather was dry and not too cold I felt it was a good time for an afternoon ride. I wheeled the CB-1 out of the garage on to the driveway. I noticed 1 tsp. of oil on the garage floor. It's been 3 weeks since I took her out. I figured I'd have to check this out when I had more time. For now I wanted to ride.

I put the choke on and she started on the first try. That's kinda rare actually. So far so good. I walked away to grab my boots and gather my tank bag.

About 90 seconds later I walked back to the bike. It was then that I saw smoke wafting up from under the tank. Lots of white smoke. Was it steam or actual smoke? I suspected a coolant leak or dripped oil burning off the exhaust. Looking closer there was way more smoke than that and it smelled like burning plastic. That's when I noticed :mortifer inside beneath the tank near the rear shock!!!

I shut the bike off and tried to blow the flames out :troy. No luck. Trying to remain calm I tried to remove the seat but I couldn't get it off (CB-1 seat removal is fiddly under normal conditions and harder under duress). Panic setting in I ran to the garage but couldn't find the fire extinguisher (I later found it hanging on the wall where it has always been for 15 years but I wasn't thinking clearly :rolleyes). Luckily a garden hose was nearby and I used it to douse the flames. arty

Aftermath: Black soot covered the tank sides but luckily wipes off easily. Inside there is melted plastic and the paint on the underside of the tank got scorched. Part of the vinyl seat cover excess near the staples got burnt. Honda use flame retardant vinyl and it smolders rather than burns. Luckily the tank fuel line that scorched didn't burn through...that would have been really ugly. The front left corner of the battery also got melted but no acid leak. Other parts are melted and burnt but I don't know their function. I feel fortunate that this all happened on my driveway and not while riding.

Question: This ever happen to anyone else? What could or should have done to avoid this? I don't know the CB-1 so well so I guess I have yet another project. I feel it might be electrical since the bike wasn't running for more than 2-3 minutes so the engine shouldn't have got that hot, right? My CB-1 has always been a reliable and fun bike so I'm feeling bummed but mostly feeling fortunate that it wasn't a complete loss.

 

[doc4216]

Glad it wasn't worse and you weren't on it when it happened!

 

[Junkie]

Based on location (nowhere near the exhaust) I agree that electrical is the most likely option.

 

[Whammy]

Glad you got ahead of it before it got worse.
If anyone can fix it you can.:thumbup

 

[Gary856]

Don't know what happened, but now I think I need a fire extinguisher in the garage.

 

[Aware]

Wow. That poor little baby. I hope it gets well soon!

 

[RVFRick]

Glad it wasn't worse and you weren't on it when it happened!

Yeah, could have been a lot worse.

Based on location (nowhere near the exhaust) I agree that electrical is the most likely option.

I'll need to investigate. I'll check fuses first. If it was fuel I think I would have lost the bike.

Glad you got ahead of it before it got worse.
If anyone can fix it you can.:thumbup

With my only runner now dead* EDIT I will be forced to go back to wrenching or find a shop to look at it. This was a serious incident.

Don't know what happened, but now I think I need a fire extinguisher in the garage.

Cheap insurance. Just make sure you mount it in an obvious place. Mine was hidden behind sports equipment mess in the garage.

Wow. That poor little baby. I hope it gets well soon!

Thanks. I have limited space at my home garage so I might have to get the bike towed.

*EDIT Ashamedly I forgot about Bessie, my Passport C70 faithful for 35 years. Still loves to romp. Easter day we cruised twisties to Pescadero Beach via PMR, Alpine & Pescadero Crk.

 

[bcj]

Possibly corroded contacts in a connector.
The SV is famous for melting the green connector behind the headstock.
The main power runs through it to the keyswitch.

Corrosion builds up over the years, which raises resistance and eventually melts the surrounding plastic.

Cleaning the pins and stuffing with dielectric grease slows the infiltration of humidity and free oxygen.

 

[matty]

First off, I'm glad it wasn't worse! I have to think there was a petrol leak somewhere, dripping from the petcock? Or maybe at the fuel pump? It may have sparked from the harness, but to have a fire like that, I would think it would need more fuel than the rubber/plastic on the harness.

I was going to pose this barf anyway: I've been thinking about using Nomex as a heat shield for my battery and it occurred to me that it might be a pretty good fire retardant, what's Barf's opinion?

 

[Whammy]

First off, I'm glad it wasn't worse! I have to think there was a petrol leak somewhere, dripping from the petcock? Or maybe at the fuel pump? It may have sparked from the harness, but to have a fire like that, I would think it would need more fuel than the rubber/plastic on the harness.

I was going to pose this barf anyway: I've been thinking about using Nomex as a heat shield for my battery and it occurred to me that it might be a pretty good fire retardant, what's Barf's opinion?

Why not go to Dupont's web site and see.
Then maybe you can draw a more informed conclusion?
https://knowledge.nomex.com/heat-and-flame-hazard

In my many years of aviation I have seen many a hot fire (none involving myself) thank god.
Some the victims survive some did not but the areas covered in Nomex did not burn.
Keep in mind these were mostly intense flash fires.

 

[canyonrat]

WOW. A mechanic should be able to CSI it.

 

[auntiebling]

I'll also guess electrical.

Getting an approximate location to where the fire started is a big clue. Something may have been on the edge of shorting out for a long time and finally did it, completely unrelated to sitting during some unusually rainy weeks.

I k ow they're an uncommon bike in the us but you might get lucky and find an unmolested harness on Ebay etc. Be careful of harness from outside the U.S. as they have different options (running lights, headlight off switch etc) that will make life a little harder swapping. I mention this because my experience is that fires always crate more shorts when insulation melts etc.


Re easy stsrt: your carbs need a cleaning. I say this because I've had 2 cb1s. Both were cold blooded and made no power below about 5k rpm until they were warm. One of them was sold to a local guy I ran I to about 5.months ago. We chatted, said he had the carbs professionally rebuilt and it starts instantly all the time and has power all across the rev range... for a 400 at least.

 

[dravnx]

First off, I'm glad it wasn't worse! I have to think there was a petrol leak somewhere, dripping from the petcock? Or maybe at the fuel pump? It may have sparked from the harness, but to have a fire like that, I would think it would need more fuel than the rubber/plastic on the harness.

I was going to pose this barf anyway: I've been thinking about using Nomex as a heat shield for my battery and it occurred to me that it might be a pretty good fire retardant, what's Barf's opinion?

Your trying to bandaid a non problem. A properly maintained bike doesn't need any kind of heat shield unless there is a known problem. There are better materials then Nomex for this application. Thermotex is a popular one.

 

[RVFRick]

First off, I'm glad it wasn't worse! I have to think there was a petrol leak somewhere, dripping from the petcock? Or maybe at the fuel pump? It may have sparked from the harness, but to have a fire like that, I would think it would need more fuel than the rubber/plastic on the harness.

My best (lame) fuel source analogy is the fire was like the top of a muffin in the oven which caught fire and was burning. It wasn't super vigorous but strong enough. I couldn't blow it out and there was a lot of smoke pouring out.

Possibly corroded contacts in a connector.
The SV is famous for melting the green connector behind the headstock.
The main power runs through it to the keyswitch.

Corrosion builds up over the years, which raises resistance and eventually melts the surrounding plastic.

Cleaning the pins and stuffing with dielectric grease slows the infiltration of humidity and free oxygen.

I must be wrong but I thought contact resistance should "simply" melt plastic and/or hopefully blow a fuse, not start a fire :mad

Cleaned contacts and grease would be ideal.

I'll also guess electrical.

Getting an approximate location to where the fire started is a big clue. Something may have been on the edge of shorting out for a long time and finally did it, completely unrelated to sitting during some unusually rainy weeks.

I know they're an uncommon bike in the us but you might get lucky and find an unmolested harness on Ebay etc. Be careful of harness from outside the U.S. as they have different options (running lights, headlight off switch etc) that will make life a little harder swapping. I mention this because my experience is that fires always crate more shorts when insulation melts etc.

Re easy stsrt: your carbs need a cleaning. I say this because I've had 2 cb1s. Both were cold blooded and made no power below about 5k rpm until they were warm. One of them was sold to a local guy I ran I to about 5.months ago. We chatted, said he had the carbs professionally rebuilt and it starts instantly all the time and has power all across the rev range... for a 400 at least.

Carbs might need cleaning but power was okay as far as I know. A new harness maybe necessary. I need to get the tank off and get an overview of the extent of damage. Hopefully I'll be able to pinpoint the source.

The previous owner told me about the fuel pump. He said it uses points and said if there ever was a fuel issue he'd check there first. David Silvers sells a points repair kit so it maybe a weak link in the design.

Lastly, I posted to the FB CB-1 group last night and already two others said they had similar experiences, one recently :wtf. Maybe there is a design flaw with the bike's fuel pump. :cry

 

[Lewd_Ferrigno]

Looks like an electrical fire. If you can find the hottest point (where the most melted stuff is) you can generally get a good idea of where it started.

The oil is just coincidental, IMHO. Plus, an oil fire would be would have telltale smoke and smell.

Another thing to consider, and this is a known Honda issue, is the regulator/rectifier. Don’t know where it is on a CB-1, but they notoriously run hot and burn out. I’ve been through 2 on my CBR

 

[matty]

There are better materials then Nomex for this application. Thermotex is a popular one.

Thanks, I've had other bikes that had thermotec, I didn't know what it was called. And the reason I was asking, I'm putting together a bike and there will be a confluence of heat sources right at the battery and I just wanted to be safe.

And OP, best of luck, hopefully the harness isn't too badly damaged.

 

[GB500guy]

Hey Rick, glad you caught it early! As others have suggested take a close look at the fuel pump. If the gas level was down below Reserve level and the fuel valve was only set to On, then the pump would have been sensing low pressure and would have been repeatedly pulsing. The contact points could then have overheated (especially if slightly corroded) and ignited a bit of fuel seepage. Old fuel lines often have small cracks that just seep but don't leak a steady stream. Could your tank level have been low?

I have the habit of shutting off petcocks on my bikes a quarter mile from rolling into home just to draw down the carb levels and reduce gas evaporation fumes in the shop. But if I do that too early on the CB-1 the fuel pump is unhappily running dry as I roll in the door. Can't be good for it. Just thought...

-Bill

 

[RVFRick]

Looks like an electrical fire. If you can find the hottest point (where the most melted stuff is) you can generally get a good idea of where it started.

The oil is just coincidental, IMHO. Plus, an oil fire would be would have telltale smoke and smell.

Another thing to consider, and this is a known Honda issue, is the regulator/rectifier. Don’t know where it is on a CB-1, but they notoriously run hot and burn out. I’ve been through 2 on my CBR

Thanks. Will do an inspection this weekend. Agree oil is a red herring for now. R/R I've heard about this a lot for various bikes. What is the best fix just get a new one and replace as a maintenance item?

And OP, best of luck, hopefully the harness isn't too badly damaged.

Thanks. I hope the harness is recoverable.

Hey Rick, glad you caught it early! As others have suggested take a close look at the fuel pump. If the gas level was down below Reserve level and the fuel valve was only set to On, then the pump would have been sensing low pressure and would have been repeatedly pulsing. The contact points could then have overheated (especially if slightly corroded) and ignited a bit of fuel seepage. Old fuel lines often have small cracks that just seep but don't leak a steady stream. Could your tank level have been low?

I have the habit of shutting off petcocks on my bikes a quarter mile from rolling into home just to draw down the carb levels and reduce gas evaporation fumes in the shop. But if I do that too early on the CB-1 the fuel pump is unhappily running dry as I roll in the door. Can't be good for it. Just thought...

-Bill

Hi Bill, thanks for the support. Yeah, wish only I acted faster and found the extinguisher right away. My face was right against the tank trying to blow out flames that were kababing the fuel line. Had the line burnt through I could have lost my eyebrows or worse :wtf

The tank was full. My habit is 1.5 blocks from home petcock to OFF to mostly empty bowls.

I don't know fuel pump anatomy. When you say contact points you are referring to the points that actuate the pump (like points on a distributor)? Here is a photo of a points repair kit.


*EDIT* service manual diagram shows fuel pump and filter position on bike. The same place where I had the fire.

 

[GB500guy]

...I don't know fuel pump anatomy. When you say contact points you are referring to the points that actuate the pump (like points on a distributor)? Here is a photo of a points repair kit.
View attachment 517773

Yes, they are electrical contact points that make or break to maintain fuel pressure to the carbs. So they are a source of sparking especially if worn and corroded. First place I would look after a fire in that area.

-Bill

 

[GB500guy]

Also be sure to check the two drain hoses that connect under the tank. Make sure they are connected and not cracked. The small one is the tank air vent and the larger one drains any leakage or spilling from the cavity surrounding the cap. If either is missing/damaged a small amount of gas or fumes would be present right where your fire was.

-Bill