Leaner or richer at higher altitude?

[Rick]

I could swear that the reading I've done says to richen for higher
altitudes but I came across Steve Fortner's Jetting guide that I had
saved from whenever and it says to lean out when going higher.
My bike seems to bog a little off the bottom when I ride in the desert
@ about 3500 ft. but rips at any RPM around 1500 ft.
Any suggs. appreciated.
Gobble gobble.....CHOP!

Rick So.Cal
'00 YZ250
'01 PW50 (son)
"It is not shameful to ride the Pee Wee
track as long as your Pee Wee is with you."

[Chris Buckley]

Higher altitude means less air density, therefore less fuel is needed.
ergo higher altitude means leaner jetting.
Chris

[Mark S. Jennings]

> I could swear that the reading I've done says to richen for higher
> altitudes but I came across Steve Fortner's Jetting guide that I had
> saved from whenever and it says to lean out when going higher.

Bikes run richer at higher altitudes (less air so a richer fuel air
mixture), so you need to jet them leaner.

> My bike seems to bog a little off the bottom when I ride in the desert
> @ about 3500 ft. but rips at any RPM around 1500 ft.

Sounds like the bogging is because you're running rich at the higher
elevation. Since it is easy to do, I'd just go up a clip position on the
needle next time and see if this improves it.

- Mark

[BigBore]

Your bike runs richer at high altitudes, so use leaner jetting.

[tmc]

Lean means to much air (too hot), rich means to much fuel not enuf air
(too cold, such does the choke on a bike). The higher you go
(altitiude wise), the richer the mixture becomes. Adjust accordingly.

2 Strokes, are quite weird, when you get down to the bottom of the
tank, just by using fuel, the less oil you have. So at the end of the
run, your bike WILL be running hotter than with a full fuel tank. You
can probably expect higher rev's more power etc, but trust me, this is
not a good thing. Less Oil equals, a damaged engine in the long run.

tmc

On Wed, 21 Nov 2001 03:31:51 GMT, REMOVETH...@bigfoot.com (Rick)
wrote:

[Rick]

On Wed, 21 Nov 2001 03:31:51 GMT, REMOVETH...@bigfoot.com (Rick)
wrote:

>I could swear that the reading I've done says to richen for higher

>altitudes but I came across Steve Fortner's Jetting guide that I had
>saved from whenever and it says to lean out when going higher.
>My bike seems to bog a little off the bottom when I ride in the desert
>@ about 3500 ft. but rips at any RPM around 1500 ft.
>Any suggs. appreciated.
>Gobble gobble.....CHOP!

Thanks for the responses guys.

[David Levy]

Dare I ask what this means? So......... according to this I should ride
with a full tank all the time?

"tmc" <t...@carrari.org> wrote in message
news:3bfb66f5....@news.sf.sbcglobal.net...
><snip>

[Tim Harrell]

tmc wrote:
>
> Lean means to much air (too hot), rich means to much fuel not enuf air
> (too cold, such does the choke on a bike). The higher you go
> (altitiude wise), the richer the mixture becomes. Adjust accordingly.
>
> 2 Strokes, are quite weird, when you get down to the bottom of the
> tank, just by using fuel, the less oil you have. So at the end of the
> run, your bike WILL be running hotter than with a full fuel tank. You
> can probably expect higher rev's more power etc, but trust me, this is
> not a good thing. Less Oil equals, a damaged engine in the long run.
>
> tmc
>

Dude, put down the crack pipe and back away slowly. The oil is mixed
into the gas, so unless you are using some totally inappropriate oil
that isn't soluble in gasoline, the oil will be evenly distributed
throughout the fuel tank. Going by your logic, if you put a larger gas
tank on your bike you would almost certainly blow up the motor before
you ran out of gas. I've run out of gas, several times (shut up, Joe),
and never had an engine failure from it, or even noticed my bikes
running different up to the last few drops from the tank when the bike
is starving for fuel.

Tim H.

[Dave Sparkman]

t...@carrari.org (tmc) believes:

>2 Strokes, are quite weird, when you get down to the bottom of the
>tank, just by using fuel, the less oil you have. So at the end of the
>run, your bike WILL be running hotter than with a full fuel tank. You
>can probably expect higher rev's more power etc, but trust me, this is
>not a good thing. Less Oil equals, a damaged engine in the long run.
>

Me theenks you are full of sheeet.

-Dave-
YZ 125
TSCEC # 432
RMEC # 3030

[Jay C]

"David Levy" <dlevyneg...@pobox.com> wrote in message
news:g3MJFypc...@rmsv06.resmec.net...

> Dare I ask what this means? So......... according to this I should ride
> with a full tank all the time?

Obviously. Sheesh.

Jay

[Pobirsm]

Correct,go leaner as you go higher I.E. less oxygen.My experience is 2 strokes
are more finicky.I have lived in and around the Sierras for the past couple of
decades and I ride between 4,000 to 11,000 feet in the same day .A fuel
injected dirt bike(trail not MX). could be a good thing

[Eric]

tmc wrote:

> Lean means to much air (too hot), rich means to much fuel not enuf air
> (too cold, such does the choke on a bike). The higher you go
> (altitiude wise), the richer the mixture becomes. Adjust accordingly.
>
> 2 Strokes, are quite weird, when you get down to the bottom of the
> tank, just by using fuel, the less oil you have. So at the end of the
> run, your bike WILL be running hotter than with a full fuel tank. You
> can probably expect higher rev's more power etc, but trust me, this is
> not a good thing. Less Oil equals, a damaged engine in the long run.
>
> tmc

Excuse me, the less oil on a 2-stroke, the RICHER! it runs. More oil =
less fuel = leaner. Less oil = more fuel = richer. Ask anybody that knows
what they are doing w/ jetting and they will tell you. Remember, oil
doesn't burn. The same volume is passed into the combustion chamber,
whether is has more or less oil in it, this volume is always the same.
That is why more oil results in a leaner condition-less fuel to burn.
Eric

--
00 XR250R
00 DS 80
74 MR50 (original owner)
01 PW80
01 Lakota
Remove "spam" from reply-to

[MVCronk]

Ya beat me to it.... :-)

Mark

[Chris Buckley]

Well you're sort of right, what really happens to fuel when you change
the oil ratio is that you change the viscosity of the mixture, I.E.: the
thicker you make the fuel by adding oil, the more resistance there will
be as the mixture is drawn through the jet, therefore a leaner air/fuel
ratio.
Chris

[Eric]

Chris Buckley wrote:

What? Hahahaha, relight your crack pipe. Idiot.

[Chris Buckley]

Never studied Physics, did ya Slappy.

[Eric]

Chris Buckley wrote:

> Never studied Physics, did ya Slappy.
>

Obviously you didn't. If you used your head for more than just a place to
hang a helmet you would realize that the viscosity difference between, say
a 25:1 and say 40:1 ratio is so negligible in terms of the diameter of the
jetting in a carb it is a non-issue. It is the same as arguing whether
water or a water/lemon juice mix will flow faster through a garden hose.
The reason less oil = a richer mix is as I stated before: more fuel in the
same volume in the combustion chamber. We will repeat this in very simple
terms. The same volume passes through the jetting in the carb, whether you
are running 25:1 or 35:1. At 35:1, more of the volume is fuel, resulting
in a richer condition. At 25:1, more of the volume is oil. Since oil does
not burn (for all intents and purposes-of course some does or it wouldn't
be a "2-smoker") there is less fuel in the combustion chamber, this results
in a lean condition. This is a long established fact my friend. So
"Slappy", I would suggest that you move south, the warm climate may help
elevate your IQ to something above room temperature in a morgue.

[Chris Buckley]

Eric, since you do not have the ability to see more than part of an
overall picture and have to resort to to a constant barrage insults to
reinforce your position, I will not debate this issue with you further.
Chris

[Eric]

Chris Buckley wrote:

Whatever bro, seems like a weasily way to admit you don't know what you're
talking about. Oh well