Why that Mountain riding hits so hard:
Sub-stratospheric conditions above 3000 Meters, robs your engine's power output a full 34 %,
due to a combination of lowered oxygen levels,
and a significant reduction in atmospheric pressure values at altitude.
# 1.
Oxygen tends to settle to low places, due to atomic weight molecular theories and gravity.
Oxygen levels found at 1500 Meters are a full 14% less than levels found at sea-level.
At 3000 Meter this percentage loss of oxygen now approaches 30%.
As carburetor jets remain fixed, the diminished oxygen in the thin mountain air will burn poorly with the carb's fixed amounts of fuel.
The logical outcome is heavy smoke from the tailpipe, and poor mileage, and significantly reduced power outputs.
Hold on though, you are about to discover the second power robbing aspect associated with high altitude engine operations...
# 2.
Concerns atmospheric pressure that we too often underestimate.
Its easy to do, most people live at elevations below 150 Meter and are essentially at sea level.
This is our normal condition to live and breathe in deep, rich, heavy air.
Atmosphere pressure is proportional to the weight of all the above molecules resting and pressing down to the bottom from miles above.
Remember diving to the bottom of a swimming pool, how with increasing depths, the extra water pressure hurts your ears.
Atmospheric pressure is alot like the collective height / weight of the water molecules, but instead we are talking about air molecules.
We are quite accustomed to life at the bottom, under the weight of miles of air molecules that are stacked above you.
Now consider the opposite, we will experience the absence of the two miles of air molecules,
the ones we left behind and below us when we riding upwards in the mountains.
Air pressure differentials are what lifts a hot air balloon and its heavy gondola off the ground.
Let's return to situation back underneath our hoods.
It follows then that less of air molecules resting and pressing above our throttle plates at 3000 Meters will fill our motor's cylinders less effectively when the piston travels down.
( Furthermore, this slower fill rate is now at odds with the sea-level 4-stroke designed camshaft timing values.
The mechanical time the valves are open will remain the same, yet due to the reduced atmospheric pressure, far less mixture will enter the cylinders.
Clearly this will remain the key power robbing component that we will be least able to compensate for with our adjustments ).
2-stroke motors use ports in the cylinder wall to time air flows and these ports are the equivalent of the 4- stroke's camshaft.
The 2-stroke is so dependant on heavy sea-level pressure differentials,
that at altitude, intake, transfer, and exhaust back pressures,
will be disproportionately disrupted,
robbing the 2-stroke stroke motor of greater torque than 4-stroke motors.
