Topic: My 1976 CB550F blew up. [with photos]

[Rigid]

Sorry for your loss, I doubt anything but the immediate application of an extinguisher could have saved it so getting off and away was wise.  There are plenty of potential spark points behind the carbs if the wind blown gas ended up back there.  Any electrical connection would be suspect. A buddy of mine had a massive fuel leak on his Yamaha and as we pulled into a gas station to check it out he was engulfed in a cloud of superheated gas vapors from fuel draining on the cylinders.  One spark and he would have been a flame ball.  Scary stuff. 

[dhall57]

When I saw the subject heading - CB550F blew up, my first thought was your engine locked up or came apart etc. Than a saw the picture and realized it was your 550 ablaze WOW!! Eveyone here is so glad your OK.  I bet in the next couple days there's going to be a lot of checking of petcocks, fuel lines and a few other things. I know I'll be checking out my bikes.

[wedoo2]

It's funny the things that memories are made of.  Hopefully yours will be the hours you spent putting that pretty thing together.  You know, when a piece fit and looked great.  How you couldn't stop taking a look at it.  Hard works' reward is in the pride it gives you.  Things come and go, but you can't take that away, so don't put your pride in that thing you had, but rather the accomplishment.  Gonna last longer.

And the memories for those who love you are not "that damn motorcycle killed him".

[toytuff]

Unbelievable.

Very lucky man. Very.

tt

[grcamna2]

    Save the rolling chassis; a titled frame is hard to find at times.

[Hondawggie]

Man, I'm putting tiny hose clamps on all my gas lines at both ends from this point forward, I'm grabbing a handful at the hardware store.  That is a painful deal man, real freak accident but you have helped some of us by knocking some sense into the risk -- I don't know where/if there was a spark source on your bike but if you size up the 'heat zones' on the remains, the very hottest spot was carb #1.  Some spark source around that area ignited gas from a leaking petcock or loose or cracked gas line.


That is a scary deal there.   I am doing 100% new gas lines, hose clamps and checking for moisture around the petcock after seeing your photos.  Seems to me that even if you had tried, you can't *easily* find a spark source -- if the bike's electrical seems find and she's running you would not even think there was an electrical issue.    Only thing you can do here is what the others have said -- assume there could be a spark source and eliminate all possibilities of leaking gas.

I don't know if I wouldn't have stood there trying to get the tank off and ended up as a smoked hillbilly.  Took guts to let her go like you did, congratulations on beating Charles Darwin at poker!

[Rigid]

    Save the rolling chassis; a titled frame is hard to find at times.

Salvage title now, insurance was involved. 

[d9canada]

I use hose clamps but an outboard guy told me they use zap straps instead, claims they can get a better all-round cinch on small diameters.

One question that was posed and I didn't see the answer - did the carbs have overflow tubes in place? 

Also if an inline filter was used, the plastic things do separate one in a gazillion times.. happened to me when a brand new 'PHSRAM' opened up in a tandem truck on a back country road.  The only thing worse than the smell of burning human hair is when the hair is your own.

Glad you are OK, get 'nother bike and move on.

[cameron]

NNNOOOOOO!

Those pictures literally brought tears to my eyes.
I have your sister-bike.. and we will ride a memorial lap for you today.

[mono]

Seeing this almost made me puke.  I'm glad youre ok, but it is so sad.   

[heffay]

That is awful, I'm sorry for your loss.  Can we all have a moment of silence?

I use hose clamps but an outboard guy told me they use zap straps instead, claims they can get a better all-round cinch on small diameters.

I use wire ties.  I don't mean zipties, I'm talking like racing wire tires.  When you're in a pinch, paper clips work fine too, just have to be more careful as they're brittle if you twist them too much.  Anyway, shade tree stuff, I prefer to go stock parts if possible. 

[Rigid]

I use hose clamps but an outboard guy told me they use zap straps instead, claims they can get a better all-round cinch on small diameters.

One question that was posed and I didn't see the answer - did the carbs have overflow tubes in place? 

Also if an inline filter was used, the plastic things do separate one in a gazillion times.. happened to me when a brand new 'PHSRAM' opened up in a tandem truck on a back country road.  The only thing worse than the smell of burning human hair is when the hair is your own.

Glad you are OK, get 'nother bike and move on.

 Hose clamps for fuel injection lines are the best choice, they compress the perimeter without bunching or pinching and provide superior clamping pressure compared to a worm gear hose clamp.  Slightly more expensive than the garden variety hose clamp but neater, and superior mechanically.

[Don R]

Oh Dude.

[VTCBike750]

Sorry for your loss. My first bike a 77 550, great bike! Had a few gas leaks while riding too. Once the float bowl drain screw wouldnt close. Another time the fuel line got perforated.

It would amazing if you rebuilt her back to her glory.

Im not running hose clamps on my bike at all and feel confident riding. Brand new hoses. Never had a problem. Maybe its time to get some though.

[BobbyR]

I can;t tell if you can salvage the bike, but it may be possible. The one thing you can;t salvage is the time and care you put into making such a beautiful machine.

I use Tygon fuel line which is self clamping and needs to be cut off.

[Psychonaut]

All I know, is that I'm grateful to God that I'm alive and not even slightly burned.

He must have just had a thing against your bike.

[CycleRanger]

Wow!    

I mean, holy cow!

Thank goodness you weren't hurt, sorry about the bike. 

[MoMo]

What may have happened is a pinhole in the fuel tank. Happened to me on my Silverwing- the pinhole was right over the left cylinder   Thankfully, I got home without self-immolating and was able to switch tanks and get the pinholes repaired...Larry

[fmctm1sw]

Dibs on the tappet covers!   j/k   Sorry man.  I can't even imagine a fate worse than that...

[jorwesflow]

One question that was posed and I didn't see the answer - did the carbs have overflow tubes in place?

Yes, I absolutely had them hooked up and running to the factory specified area. But one thing to note was that carb #2 had been leaking out a few drips of gas around the bowl gasket for a little while, but only if I leaned the bike. I posted this thread several months ago because I had stripped the threads on carb #2 and was asking for advice on what to do: http://forums.sohc4.net/index.php?topic=91070. I went with 12mm screws that reached in further and grabbed more of the threads that weren't stripped, and the bowl seemed to tighten down pretty well, but it still would drip every once in a while.

I started noticing a tiny amount gas sitting on the top of the crankcase if left the bike on the side stand for several minutes. So I had been only using the center stand until I got around to fixing that drippy carb bowl. I had also recently rebuilt the carbs with all new gaskets, parts, etc and I wasn't jumping at the opportunity to dig back into them. I really would hate to think that's what caused this. Not sure how a few drips of gas could have caused the inferno, but that's all i got for theories right now.

If that was indeed the cause, I guess there's a moral to the story: don't underestimate the potential danger of leaking fuel, even if it's just small intermittent drops.

[Terry in Australia]

All I know, is that I'm grateful to God that I'm alive and not even slightly burned.

He must have just had a thing against your bike.

Of course he does, everyone knows that God rides a CB750 mate,.................

[Spanner 1]

What a disaster !... sorry to read this, but glad your O.K..... my 2c would be fuel dripped into the starter motor cavity and your bike actually caught fire in the starter compartment and 'licked' up to the carb bowls. The starter produces micro sparks from the brushes when you crank it and could certainly ignite a fuel/air mix which had seeped into the st. mtr. housing.... who knows 

Re-read your 1st. post... happened after 2 miles of riding .... not the above explaination then

[bjatwood]

Very Sorry to hear of your bike fire.
Glad that you didn't get burned 
Remember...Bike's can be replaced, people can't!

[RRRToolSolutions]

You know, I read this thread's title and immediately was skeptical - almost didn't open it. Very few engines "blow up" and those usually have some supercharger on them going down the dragstrip..

Yours is truely "blown/burnt -up". Man, I hate it for you. I will assume there is no insurance, so if you decide to replace - do post and let us know. I would for one donate parts or funds to help the replace. I don't offer to help folks too lazy to help themselves or who just plain abuse/tear their stuff out of neglect and abuse - yours is some real bad luck and you had put time into it -

Gordon

[jorwesflow]

my 2c would be fuel dripped into the starter motor cavity and your bike actually caught fire in the starter compartment and 'licked' up to the carb bowls. The starter produces micro sparks from the brushes when you crank it and could certainly ignite a fuel/air mix which had seeped into the st. mtr. housing

i had thought of this, but ruled it out for the exact thing you said... i was already down the road. i doubt i'll ever know what really happened!