Gasoline - how easily ignited?

I reinstalled my fuel tank recently and splilled a little fuel onto the
headers when connecting the fuel line. Wiped it dry and when I started
the bike the fuel vapors started smoking a little.

I was told this is not a concern as the ignition temperature of
gasoline is very high (like close to 300F) and it will not catch fire
without a spark even if the headers get very hot... any truth to this?

 

Any truth to what part?

"this is not a concern [the smoking header]"
probably true. If your bike didn't light up the first time, it's
unlikely to light up later on. Whatever was there has either evaporated
or burned off by now. I wouldn't make it a matter of habit to slosh
gasoline around though.

a search on the ignition temperature of gasoline brought up the
following, which agrees with my own recollections, more-or-less:
http://hypertextbook.com/facts/2003/ShaniChristopher.shtml

from the above: spontaneous ignition temperature of gasoline: 536F
piloted ignition temperature: -50F

So, gasoline might have a high spontaneous ignition temperature, but it
will light in the presence of some other ignition source at _extremely_
low temperatures. It doesn't take much of a spark to ignite gasoline
(just ask Kaybear, or better yet, search for his posts on spark plugs
and coils). It wouldn't take much of an exhaust leak to introduce the
potential for a fireball.

Of course, I also don't know how hot things like your exhaust headers
actually get, so even if the spontaneous ignition temperature is high,
it's possible (but again, I really don't know) that you could exceed it
on certain engine components at some times.

 

I've spilled oil on hot car headers and had that catch fire. I imagine
if oil will ignite, gasoline will, too.

 

This is odd because oil lubricates at far higher temperatures inside
the engine. According to Mobil 1 it says the oil does not break down
until 400F. Quite bizzare.

 

I enjoyed this statement from the above link: "Gasoline is the most
common flammable liquid and the main cause of injuries among teenage
boys."

much of a spark to ignite gasoline (just ask Kaybear, or better yet,
search for his posts on spark plugs and coils).

It's the vapors that burn, not the liquids. Anybody who has studied
fire science knows that wood, or coal, or so-called "flammable liquids"
don't actually burn, it's the vapors that burn, once the fuel is heated
to ignition temperature...

I worked at a waste water treatment plant once. We had a big vessel
with a burner underneath a bed of ordinary sand. We would heat up the
sand to about 1400 degrees and start forcing dried sludge powder
through the hot sand. The sludge powder would start smoking, and the
smoky vapors were what actually burned. We forced the heat from the
fire through a boiler, made steam, and drove a steam turbine generator,
and it was all powered by---partially-digested and dried human shit!

Incredibly weak sparks will light off a combustible mixture, or even
cause an explosion if the mixture is just right. Various gases have
upper and lower levels of explosibility, and we used to have to "sniff"
vessels in the refinery before we could work in or around them. We used
a meter called a "Mine Safety Appliance" to sniff for flammable
hydrocarbons before anybody could go inside a tank or other vessel that
had contained flammable hydrocarbons...

And, out on the flightline, when I worked on airplanes, the fuel truck
drivers would have to hook up cables to discharge static electricity
from their truck and the fuel nozzle, before they could touch the
nozzle to the aircraft, which was grounded too, by its own cable...

Everybody has experienced static electricity discharging as they pet
their cat on a cold dry day, or walk across a rug and touch a doorknob,
or slide across their car seat to touch something metal in the car.
There's not much heat energy in static electricity, but it can and will
ignite flammable vapors...

Technicians who refuel airplanes take every precaution to avoid static
electricity fires...

actually get, so even if the spontaneous ignition >temperature is high,
it's possible (but again, I really don't know) >that you could exceed
it on certain engine components at some times.

You may have seen photographs of exhaust headers glowing red after
long hard dyno runs. That's at least 700~800 degrees F...

 

the headers when connecting the fuel line. Wiped it dry and >when I
started the bike the fuel vapors started smoking a little.

I can think of two possibilities for what the smoke actually was, since
gasoline vapors would be colorless and invisible...

Was it *white* smoke?

One possibility is that the gasoline washed some *oil* which had
previously wept from your valve cover gasket onto your headers, and
that is what smoked...

The other possibility is that the gasoline dissolved some of the
coating on your header and the *coating* is what smoked...

Every once in a while, when I get tired of the rust specks on my
Yoshimura header, I will pull it off and re-paint it with high
temperature barbecue paint. That stuff will smoke the first time I warm
up the engine, if if I let the bike sit for a week...

So far as fires on motorcycles are concerned, the only time I can
remember having a gasoline fire is when my Yamaha engine started
dieseling and I pulled the fuel hose off the petcock to try to stop it
from dieseling at high RPM. I don't remember whether I pulled the spark
plug wires off before yanking the fuel line off (the ignition was
magneto, with a push button kill switch). I got a little gasoline fire,
for just a second, because about a tablespoon of gasoline hit the
cylinder...

 

I know tranny fluid will ignite easily, with the help of a spark. I worked
at a gas station in the mid-70's and someone brought in an old squad car and
asked me to check the tranny fluid level. I accidentally brushed against a
gizmo mounted on the wheel well as I was withdrawing the dipstick and it
went up like a flaming sword. Lucky thing I didn't send the whole station
to kingdom come.

 

and the problem was a major oil leak onto the exhaust system.

I had an old beater Dodge once. Oil was leaking out from under the
valve cover gasket onto the exhaust manifold and it would smoke when it
got hot. Eventually, the leak got worse and the engine caught on fire
in the parking lot of K-Mart. I saw a lot of white smoke coming out
from under the hood, so I opened the hood to look...

Dumb move, air got to the fire and it got worse. I tried to smother the
fire with an old overcoat I had in the trunk, but the coat just caught
on fire, too...

I closed the hood to keep as much oxygen away from the fire as
possible...

Then I ran into K-Mart and asked the greeter for a fire extinguisher to
put out the fire. The greeter told me that I could *buy* a fire
extinguisher in the auto parts department...

I told her that I didn't have time to buy a fire extinguisher, my car
was on fire...

She said that K-Mart didn't supply fire extinguishers to customers
whose cars were on fire...

About a minute passed and the manager came out with a fire
extinguisher, put the fire out and apologized for her ignorant
behavior. But, by that time, my ignition wires and distributor cap were
all melted...