"I am Tosk" wrote in message
...
In article ,
says...

Wilbur,
You have it almost correct, but what actually happens is that in the
hottest point in the combustion chamber, the fuel/oil mix
diesels starting a flame front, but before that flame propagates across
the piston surface, the spark sets off another flame
front. When the two fronts collide there is a very high temperature
explosion that causes the aluminum to actually melt. This can
be heard as a knock, but it is very difficult to hear in an outboard
engine. At low throttle, this can be tolerated for a few
seconds, but at high throttle, it is almost instantaneously terminal, as
much of the head and piston blows out the exhaust port as
molten aluminum. The entire point of this thread is to point out that
lube oil will lower the auto ignition point of the fuel
charge. Catastrophic damage, on the other hand is a product of chamber
temperature, fuel/air ratio, as well as the fuel mix
tolerance to auto ignition. If the engine is of the low performance
variety, fuel/oil mix tolerance will be greater, but in a high
performance configuration much more attention must be given to the fuel
mix.

Historically, the migration from the recommendation of 25:1 to 50:1
occurred with the change from plain bearings to roller/needle
bearings. Oil injectors allow even more reduction, because lubrication
can be assured at low throttle settings where lube
starvation always occurs with premix fuel. This lube starvation was the
primary driver for fat fuel/oil mixes.
Steve

"Wilbur Hubbard" wrote in message
anews.com...
"Bob" wrote in message
...
WARNING WARNING WARNING WARNING WARNING WARNING
WARNING WARNING WARNING WARNING WARNING WARNING
WARNING WARNING WARNING WARNING WARNING WARNING
WARNING WARNING WARNING WARNING WARNING WARNING

Interesting. The Outboard Shop, the local evinrude/johnson dealer,
gave me
the exact opposite recommendation.......

Fact: people forget 50% of what they hear immediatly.
In other words SKip you probablly heard, "bla bla bla recomend bla bla
evenrude bla..."

Further, my manuals for both engines show ........

Gaaaaa you have to comprehend also my selective reader.

I grant you that quadrupling the oil may have some deletorious
effects, but
my common sense tells me........ should not be a problem.

Hey sikp have you been using your BrontoThesaurus again ? Please dont
use such big words as deletorius. They sont have a Salubrious effects
on my comprehension.

Also, I've never seen oil being more subject to explosion/flash than
gasoline.

How does adding oil to fuel make it more volatile?
L8R
Skip

:: Your comment and question shows a basic lack of fuel and combustion
:: concept understanding. Will those here more knowledgable please
:: inlighten SKip. Im off to watch the 30 foot 17 second swells hit the
:: jetty.


I think Mr. Grundlach may be correct for once. Adding more oil to a
given amount of gasoline actually acts as an anti-knock
ingredient. It lowers the rate of speed at which the flame front
propagates from source of ignition (spark plug) to
cylinder/piston surfaces.

It increases the duration of the burn and thus lowers the temperature
of the burn. Add too much oil and the motor will run as if
the choke were on. I don't know of any cases where piston damage from
heat will result. The worst that will happen is the works
(piston rings piston crown) might become gummed up, the exhaust port
will become carboned up and exhaust gass passage restricted
and exhaust port opening retarded because the piston will have to
travel down several millimeters more before it reaches the
exhaust port opening. I have seen exhaust ports so carboned shut that
one could barely poke a finger through it. The engine
would not rev up and it performed like the choke was on all the time.

Too much oil is, indeed, a bad idea but not for the reasons you listed.

Wilbur Hubbard
(worked as a two-stroke mechanic for seven years and as a technical
advisor for a Japanese motorcycle company for seven years)





What motorcycle company? This year my daughter is on an '09 RMZ 250 that
was Tony Lorousso's Nationals bike last year... Bettencourts, Pro
Circuit, Factory Connection... Lowered with a Pro Circuit link, PC Pipe,
and a couple of extra toys

Last year she took third place for the season in the womens 125/250
class, working her ass off on a KX100 all season.

If you still have friends over there, we could sure use some help racing
next season Got a lot of room on the side of the "white trailer"!


--
Rowdy Mouse Racing - Pain is temporary, Glory is forever!



Yes, it was U.S. Suzuki Motor Corp. I think they've renamed it since. I used
to race motocross myself on the old TM 125 and TM 400 and then on a Maico
400. Held AMA national number 42 at one time. But, this was years and years
ago back when Hans Maisch, Heikki Mikkola and the great Joel Robert were in
their prime and I've lost contact with any and all.They're probably all
retired by now anyway.

http://en.wikipedia.org/wiki/Jo%C3%ABl_Robert

Your daughter sounds good. I wish you all well.


--
Gregory Hall