Gearing Down for Altitude: Dyno Results?

[nicholastanguma]

I'm considering purchasing a house in Mexico City in addition to my place in New York City. I ride only air cooled, carbed, single cylinder motorcycles, they're my favorite and that will never change; as such, I'll be taking a favorite moto from NYC to CDMX with me. 

But here's the issue:

While NYC is at sea level, CDMX is 7,000ft above sea level, so clearly that means anywhere from 10 to 13 hp lost at the rear wheel, and with an air cooled, carbed, single cylinder moto that's a HUGE drop in usable power.

My favorite moto is dyno tuned, so I know her hp/tq numbers on paper as well as on the street. If I simply gear down a tooth or two in the bike's final drive ratio, and then dyno tune on the same dynamometer, can I expect to keep the Mexico City variant feeling as powerful and usable as the New York City variant, albeit with a lower top speed?

It seems to me the answer is surely, "Well, obviously, yes, duh, stupid," but I want to hear it confirmed from other experienced voices in case there's something I'm missing.

[Tom68]

I wouldn't change the gearing, add compression and lean the jetting, but yer it's gunna suck.

[David Redszus]

I'm considering purchasing a house in Mexico City in addition to my place in New York City. I ride only air cooled, carbed, single cylinder motorcycles, they're my favorite and that will never change; as such, I'll be taking a favorite moto from NYC to CDMX with me. 

But here's the issue:

While NYC is at sea level, CDMX is 7,000ft above sea level, so clearly that means anywhere from 10 to 13 hp lost at the rear wheel, and with an air cooled, carbed, single cylinder moto that's a HUGE drop in usable power.

My favorite moto is dyno tuned, so I know her hp/tq numbers on paper as well as on the street. If I simply gear down a tooth or two in the bike's final drive ratio, and then dyno tune on the same dynamometer, can I expect to keep the Mexico City variant feeling as powerful and usable as the New York City variant, albeit with a lower top speed?

It seems to me the answer is surely, "Well, obviously, yes, duh, stupid," but I want to hear it confirmed from other experienced voices in case there's something I'm missing.

NYC
Baro...29.92inHg
Temp..80F
RH.....30%

Mex
Baro...22.06inHg..(7000ft)
Temp..80F
RH.....30%
Air density...-26.37%
Fuel req......-26.3%
Power loss...-30.63%

A power loss of 30% will never be recovered without a turbo.
And it will take some serious gearing changes to recover the torque loss.

[Tom68]

And it will take some serious gearing changes to recover the torque loss.

Just leave it a gear lower but you'll be going slower.

[nicholastanguma]

I'm considering purchasing a house in Mexico City in addition to my place in New York City. I ride only air cooled, carbed, single cylinder motorcycles, they're my favorite and that will never change; as such, I'll be taking a favorite moto from NYC to CDMX with me. 

But here's the issue:

While NYC is at sea level, CDMX is 7,000ft above sea level, so clearly that means anywhere from 10 to 13 hp lost at the rear wheel, and with an air cooled, carbed, single cylinder moto that's a HUGE drop in usable power.

My favorite moto is dyno tuned, so I know her hp/tq numbers on paper as well as on the street. If I simply gear down a tooth or two in the bike's final drive ratio, and then dyno tune on the same dynamometer, can I expect to keep the Mexico City variant feeling as powerful and usable as the New York City variant, albeit with a lower top speed?

It seems to me the answer is surely, "Well, obviously, yes, duh, stupid," but I want to hear it confirmed from other experienced voices in case there's something I'm missing.

NYC
Baro...29.92inHg
Temp..80F
RH.....30%

Mex
Baro...22.06inHg..(7000ft)
Temp..80F
RH.....30%
Air density...-26.37%
Fuel req......-26.3%
Power loss...-30.63%

A power loss of 30% will never be recovered without a turbo.
And it will take some serious gearing changes to recover the torque loss.

Helpful, thank you.

[Schurkey]

Don't get killed in the Mexico City Earthquake. Built on drained lake Texcoco, unstable, loose soil, and not so far from active tectonic plates.

5000+ killed in the '85 earthquake.

The bike will be the least of your problems there.

[In-Tech]

Wow, going from one of the worst places in America to one of the worst places in Mexico

I have some friends there if you would like some advice of where to live.

[Tuner]

Don't get killed in the Mexico City Earthquake. Built on drained lake Texcoco, unstable, loose soil, and not so far from active tectonic plates.

5000+ killed in the '85 earthquake.

The bike will be the least of your problems there.

More to worry about from cartels and crooked federales than earthquakes.

[mt-engines]

Wow, going from one of the worst places in America to one of the worst places in Mexico

I have some friends there if you would like some advice of where to live.

Un true. The border cities are the worst. Then Culican Sinaloa. Mexico city and Toluca are great cities. I've live and traveled pretty much all of Mexico over the past 25 years.

Just like any large city in the world, if you look for trouble you will find it.

[panic]

As air density goes down, heat removal by convection is reduced.
Don't lean it out too much.

[David Redszus]

As air density goes down, heat removal by convection is reduced.
Don't lean it out too much.

Yes, but so is the heat produced by the engine.

Get out the old O2 sensor.