My 2-cents.

First, a 50-1 mix is about 2% oil; a 25-1 mix about 4%. Yes, twice as
much oil but still very little of it. Unlike Steve, I've seen many
(not his hundreds) of 2-cycle engines seize up from too little oil,
but never from too much. Heck, I remember one guy that used 12.5-1 (2
qts. in 6 gallons) in his ultralight. Looked like he had a smoke
system! BTW, the ultralight engine manufacturers recommended 25-1 for
the first 25 hours for break in.

Not water cooled, but a real world example. About 20 years ago I built
and flew a gyrocopter. It used a WW II era 90HP, 4 cylinder engine.
The manufacgturer's recommended mix was 25 parts 130 Octane leaded
aviation gas to 1 part 40 wt. aviation (mineral) oil.

The 70's did away with the two aviation grades so the choice was 100
LL ( 100 Octane low lead ) or premium auto gas.

Most everyone also used 2-cycle oil and mixed it 50-1 because it's
mainly the oil used that determines the ratio. The 50-1 mix became the
standard shortly after the so-called "50-1 oil" came out and became
readily available, I think in the 50's.

A few folks with gryos and ultralights tried the very expensive "100-1
oil" and shortly faced engine rebuilds.

BTW, the gyro engine was high compression. I've been racking my brain
trying to remember, but am coming up blank. Anyway, that's why the 130
Octane gas.

Rick

"Rick Morel" wrote in message
...
My 2-cents.
snip.............
.. Heck, I remember one guy that used 12.5-1 (2
qts. in 6 gallons) in his ultralight. Looked like he had a smoke
system!
snip...........
Rick

Got that beat.
My 1954 British Seagull 40 Plus uses 10:1 ratio.
If there's a strong tail wind, I almost choke to death, so I constantly gybe
to keep the blue exhaust smoke on one side or the other.
BTW I don't use that engine much anymore.

On 10/25/10 8:41 PM, YukonBound wrote:


"Rick Morel" wrote in message
...
My 2-cents.
snip.............
. Heck, I remember one guy that used 12.5-1 (2
qts. in 6 gallons) in his ultralight. Looked like he had a smoke
system!
snip...........
Rick

Got that beat.
My 1954 British Seagull 40 Plus uses 10:1 ratio.
If there's a strong tail wind, I almost choke to death, so I constantly
gybe to keep the blue exhaust smoke on one side or the other.
BTW I don't use that engine much anymore.


In 1954, I recall my dad letting me have a 7.5 hp Evinrude Fleetwin on a
12' Skimmar brand skiff. The boat actually planed. Half pint of oil to a
gallon of gas.

"YukonBound" wrote in message
...


"Rick Morel" wrote in message
...
My 2-cents.
snip.............
. Heck, I remember one guy that used 12.5-1 (2
qts. in 6 gallons) in his ultralight. Looked like he had a smoke
system!
snip...........
Rick

Got that beat.
My 1954 British Seagull 40 Plus uses 10:1 ratio.
If there's a strong tail wind, I almost choke to death, so I constantly
gybe to keep the blue exhaust smoke on one side or the other.
BTW I don't use that engine much anymore.
Helps to keep the mosquitoes away I'll bet?

On Mon, 25 Oct 2010 18:48:23 -0500, Rick Morel
wrote:

Not water cooled, but a real world example. About 20 years ago I built
and flew a gyrocopter. It used a WW II era 90HP, 4 cylinder engine.
The manufacgturer's recommended mix was 25 parts 130 Octane leaded
aviation gas to 1 part 40 wt. aviation (mineral) oil.

Interesting! Do you happen to know Ken Brock? He was one of the
gyrocopter pioneers and flew one across country for the publicity.
He and I appeared together on a television show called "To Tell The
Truth" back in the early 70s. I was one of his "imposters" and Ken
of course was the real thing.

On Mon, 25 Oct 2010 22:30:42 -0400, Wayne.B
wrote:

On Mon, 25 Oct 2010 18:48:23 -0500, Rick Morel
wrote:

Not water cooled, but a real world example. About 20 years ago I built
and flew a gyrocopter....

Interesting! Do you happen to know Ken Brock? He was one of the
gyrocopter pioneers and flew one across country for the publicity.
He and I appeared together on a television show called "To Tell The
Truth" back in the early 70s. I was one of his "imposters" and Ken
of course was the real thing.

No, but I did meet him. A great guy. About all the gyrocopters used
his horizontal stabilizer and control system.

Rick