Altitude and the 4 stroke

S

Scottm

Guest
Only 10 day left till the kids the Titan and I head off to Lake City Colorado. My parents and the kids will be staying around 9,000 feet but I will be camping around 10,500 and plan on using my bike to get from the camp to the condo and just farting around up in the mountains on well maintained county roads.

Does anyone have any warnings or advice for performance issuses dealing with the altitude difference from Fort Worth to 11,000 feet.
I know I'm comparing apples to oranges, but I notice no difference when my car is up there but I don't know about the bike.
Thanks,

Scott
 

pedalpower

Member
Joined
Jun 22, 2008
Messages
92
rocky mountain high

don't know squat about the titan but go easy on the brewskis the first couple of nights,ha. less oxygen obviously, so will run rich and a litle less power after you adjust? just guessing-internal combustion basics? small engine, probably not much noticable difference-maybe run hotter?

post no. 2 just my .02 from a Coloradoan. Where is Lake City?
jon
 

jimraysr

Member
Joined
Apr 9, 2008
Messages
236
You don't say which model you have. I see they have both 2 and 4 cycles engines. You situation will depend on the type of carb. you have. Many 2 cycle have a cylinder with a metering rod attached. I have had to drop the rod down a notch or two in high altitude when I rode Yamaha 2 cycle trail bikes in the 60s. If the carb has a butterfly thottle, then you have a main jet and go smaller for high altitude. If you had a Honda you could go to a dealer and get a high altitude jet. It generally is in the bottom of the center tube inside the float bowl. They are threaded into it from the bottom. It is exposed when the bottom bowl retainer bolt is removed along with the bowl. If it is a China Honda knockoff the parts of the carb. might be interchangeable wt. Honda parts? If you have a fuel pump carb. then I think you are on your own. Honda uses a separate lift pump.
 
F

fetor56

Guest
Duane seems to be the expert in this Scott....i think u loose 1 Horsepower per 1000 feet in altitude but please don't take that as gospel,i know the figure's surprising though.
Tell Dax your plans & i'm sure he would be happy to offer advice,he lives pretty high-up doesn't he........feedback on this subject would be invaluable.
 
S

Scottm

Guest
Thanks for the input. Duane and Large live in /around Denver, which is the "Mile High" city, so that will be about half of where I'll be.
Jimray, I have the Titan 4 stroke/ Honda clone.

Well this should be a fun experiment. I'm not out for speed, since I'll be on dirt roads and won't need the motor on the downhill streches.

Lake City is in the Southwest corner. North of Durango and south of Gunnison. Only one paved Hwy in and out. There are some old mining roads that pass over 13,000 feet. It's a 4 hour 25 mile drive over the pass to Silverton.
2 years ago I climbed a 14,000 foot mountain in the dark so we could watch the full moon rise over America, then the moon light lit our path back down.
 

jimraysr

Member
Joined
Apr 9, 2008
Messages
236
So is the tank on top and gravity fuel flow or down and has a diaphragm carb. to pump the fuel up? Wouldn't know what to do on a diaphragm carb. as most of them I have seen have the jets pushed into the body and not replaceable. Again if gravidty feed, a Honda dealer might recognize the carb as a knockoff and be able to supply a jet. I have a 11 HP Honda engine on the pressure washer and replaced the carb. before I learned to drain it each time after use do to the junk in the "modern" gas which gunked it up and I took it apart so many times, just bought a new one. Anyway Sams CLub had a pressure washer wt. a knock off 13 HP engine on it and I could not tell the difference in the engines and their parts including the carb. I believe you could interchange most parts. One note is even though China might copy the design, they may not use the same thread pitch or size? Hope if you have a power problem this helps. Desperate to get my trail bike running right at only 8000 feet I filled a jet wt. solder and drilled it with a smaller mini drill while camped in the boonies. Doubt most people camp wt. all the gear we did, but it saved the trip for me (my buddy rode a Honda and had a smaller jet wt. him) I bought a new jet from Yamaha when I returned to Tucson. Jim
 
Last edited:

Skyliner70cc

Active Member
Joined
Nov 17, 2007
Messages
1,344
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.

I'm living back at sea level after living in Colorado for 5 years. I cannot believe how fast my na sports car is (na is normally aspirated).
 
Top