Toby wrote in response to my suggestion about carb icing as the
cause of the intermittent sputter some folx have experienced
during rainy rides:
> > Tom,
> > Very interesting. The air through the carb really is
hauling ass a.fwy
> > speeds huh?You may just have something here. This would
account for those
> > 'smooth' or even' power losses I think. Wouldn't it? Maybe
even some
> > 'sputtery' ones usually typical of water in 'spark system'
sort of
> > failures.If this turns out to be 'IT', I hope somehow,
someone knows how
> > to loo under wierd problem #2' in the archives.
>>
> > So recycling warm air, or some sort of carb warming
device would sort
> > this possiblity eh?
> >
> > Slide
And Bogdan added
> Warming device eh what? Kris Cichon (Mariola's squeeze,
remember her?) is
> convinced missing is caused by HOT air from the radiator
hitting the fuel
> line. He wants to install a COOLING device. Tom, if I recall
correctly,
> lives near Atlanta, no heat there. Kris lives in the middle of
Chicago,
> known for its mild winters. Wonder if location is influencing
anyone. Course
> they both could be right. Bogdan
As counter-intuitive as it may seem, icing is possible under
conditions as high as 60 degrees F - I've seen it first-person
back when cars were carbureted (practically ancient history now).
Maybe that physics professor lurking out there can explain the
dynamics of the Venturi effect? My KLR exhibited the symptoms not
in Atlanta, but in the White Mountains of New Hampshire last
week, where it was raining and in the 40's F. Can I prove it? No,
it's a transient condition and as soon as one slows heat rising
from the engine quickly warms the carb body enough to make it go
away. Mine only did it for about a mile during the coldest part
of that ride, and when I slowed for a motor home chugging up a
long climb it disappeared.
FWIW, heat-related problems usually cause fuel in the carb or
supply line to vaporize leading to hot-restart problems. I
suppose if it were hot enough around the carb to boil the fuel -
and that's increasingly likely with oxygenated fuels - one would
experience a symptom more or less like that of running off "Main"
and onto "Reserve", a rapid and complete loss of power.
It's also possible that the problem we're talking about is being
caused by roadwater intrusion into an electrical connector during
a rain. My bet would be the modular plug that connects the coil
to the wire harness. Whatever is being splashed up off the
pavement by the front wheel contains tire dust, which contains
carbon black - the stuff that makes natural rubber black instead
of that weird brown color - and enough of it in a connector and
there could be some "new" electrical pathways that would lead to
no spark. Complicated, ain't it?? What puzzles me about that
scenario, tho, is that it wouldn't be transient, so I kinda doubt
the likelihood of the roadwater intrusion explanation.
Sorry for being so wordy.
Tom Bowman
Atlanta
P.S.: Say, Bogdan - you're not Dave Swider's evil twin brother,
are you?? If you are, hope Tina's doing well....