Altitude and the 4 stroke

[Large Filipino]

Scott. When I climb big hills I give it just a bit of gas and I pedal along. You're lighter than me by a whole lot and you're running on 24 inch rims so power should not be an issue with you at all. But expect less power of course.
Man. I need to get off this hill and see how my Titan goes. It's plenty for me as it is. But as Duane mentioned,the power is amazing at sea level.

 

[Scottm]

Duane says he ran his bike at 9,000 and it worked fine.
Thanks Skyliner for the info.
Yeah, Large, I don't think my 140 lbs will bother it too much. Most of the roads are smooth dirt roads well maintained by the county and I won't go fast so i don't slip and slide all over. The main road travels along the valley floor, so I'll avoid any steep inclines. I just didn't want to haul my bike up there only to not have it work.

It will be interesting to compare the power from DFW to a higher elevation.

 

[Scottm]

Running great

Well the kids and the Titan rode well for 2 days and 800 miles, so adjustments had to be made.
Once I got here, I had to adjust the idle pretty high to get the bike started and to keep it running. The Titan has been flawless on the steep dirt roads. I do have to pedal assist from time to time, but other than that I'm having a blast. My speedo isn't working and there's no wally world or bike shop for 100 miles.

There is a fine dust on everything and when I get passed by a truck or ATV I get a good lungfull of dust.

I have to stop the bike at the top of big down hills so I can kill the motor and coast down.

My family says they can't hear the bike when I'm not close. I have been able to sneak up on some deer.

 

[Large Filipino]

I've been up there before when I shuttled for the airport. It was a Durango run.
Laws stated that I needed to stay the night once I got there for I was running too many hours so to save money I pulled to the side of the road and slept there.
That area of Colorado is beyond amazing.

 

[Skyliner70cc]

A tip for extra power at high altitudes only: Buy a quart of 20% model car fuel from a hobby fuel-quart is smallest size it is sold it. Add 5 oz to each gallon of premixed gas. Shake well and add to your fuel tank. Works great for sea level bikes not rejetted for high altitude operation. Do not use this below 5,000 feet in altitude or you will fry your engine.

With 5oz of 20% fuel per you are adding the following to each gallon of gas
a. 1 oz of nitromethane
b. .7 oz of 2 stroke oil (usually a castor/synthetic blend)
c. 3.3 oz of methanol

Not a whole lot but just enough to lean out the mixture and restore some of the lost power at altitude. This is what I added to operate at 7,000 operation. If you are going higher, you can add accordingly.

The small amount of oil in the fuel won't hurt a bit so don't even worry about it fouling the plug, it won't.

I miss Colorado......AR is ok and we canoed for 5 hours this afternoon in the Ozarks but I miss the Rockies!

 

[jimraysr]

Speaking of the dust, what does your air cleaner look like. Might be well to check? Jim

 

[Scottm]

Okay, I've made it back alive to Texas. I got about 40 miles of riding in. I stayed close to the camp grounds, since there is no cell phone service up there and no one to call for a rescue ride. I did hit a big rock sticking out of the road and that may have cause my torque strap to snap.
The bike ran great, but I had to have the idle set pretty high. The air cleaner and filter were fine.
One thing I did learn about the altitude and tires though, air pressure is a lot different. I used my same air pump that I use here in Texas. By the time the gauge got to 20psi, the tube I was inflating exploded. The 6 pack of Bud Light bottles in the ice chest all popped their caps when I went over the 13,000 foot pass, except for the bottle that exploded.
Large, it was frustrating to be in the same state and so far away. I would have loved to come meet you and Duane and gone riding on your trails.

 

[HoughMade]

Expect 3% decrease in HP for every 1000 foot gain in density altitude. This is best case assuming your mixture is appropriate for the altitude meaning adjusted or rejetted. It can be worse if carb mixture is too rich....

That right- the manual for my Honda states that you can expect a 3.5% drop in power for every 1000 feet in altitude.

 

[Skyliner70cc]

That 3-4% really adds up in aviation. I remember OH-58 pilots in Colorado who didn't have enough power to do a 3 foot hover and would hover above the ground at a 6 inch-1 foot hover and do left pedal turns only because a right pedal turn would have caused an overtorque, overspeed, or overtorque of the engine. So how did they fly their little choppers if they were hovering at almost 100% available power in the hot thin air? Easy, a heli is more efficient in forward flight than in a hover.....google effective translational lift (ETL)..its a neat feeling when a heli goes through ETL-you get a neat little shutter and the climb airspeed increases dramatically. In old aircraft with no pitch stabilization you get a nose up pitch at ETL too.

Due to the 3-4% rule, lots of heli's don't have enough horsepower available to hover out of ground effect. This means that they can only hold a hover within a vertical distance about the lengh of a rotor blade and can't stop in a high hover in flight or do manuevers that require OGE (out of ground effect) power such as pinnacle landings, etc..

This concludes your helicopter lesson for the day. Sorry, can't you tell I miss it.