250cc on altitudes?
 

I know that the altitude is a problem for the 250cc engines, but I am trying to realise the size of the problem. Is there any possibilities not to work the engine at altitudes like 15830 feet (5602 km) or it will work just slower? I read from travellers that the cruising speed will be about 25 mph. That's not a big problem for me. I am only worried, for damages to the engine because the continuous wrong mixture of air/gas.

I 'll travel from Greece to India and I don't want to miss the KKH, the Ladakh and so on. I will ride some roads at 10000 - 15830 feet. I am thinking of using a Honda XR 250 with electric start, hard luggage, solo. So, is this possible, even at slow speeds?

Hi Furious!

I did not traveled with a 250cc bike but could suggets you to drill many holes in your air box. Then close them all with put plastic or rubber plugs. As you will go higher in altitude and feel less engine power, you removed some plugs to compensate the fuel/air mixture.

This allow you to tune, at some degree, your fuel/air mixture without playing with your carb.

I have done that also on my KLR for high altitude and like it.

If you have money, you can have a look at "edelbrock carb". All ajustments on the card can be done externally. I never tried it myself but could be an interessting option for fast carb tuning on the road.

Patrick

I don't think you will have any problem. Most mountain roads only attain high altitudes over the passes before dropping altitude quickly on the other side of the pass. You will lose some power, but it will be enough to get you over. I took my R65 over some high roads in Ladakh, northern India (the highest, in fact at 5602m) and i met a guy who had just been over the highest pass on a 25 year old vespa.
You can tune your carbs i guess to make the mixture leaner, but don't forget to tune them back at lower altitude. The engine will be alright with a too rich mixture at altitude, but if it is too lean coming back down, it could result in damage. Better to leave it as it is if it gets you up there.
Sean

I found this link on a Chinese bike site. This group started out on Zongshen 200cc enduros in China. Two of the members continued for 31 days doing 10,000 km's total, and hit some high elevation with mixed reviews. I am not sure which days they went throught the mountains, but the readings are interesting, so have fun reading.

http://www.danielmontejo.com/Picture...themachine.htm

yep, i know the problem very well. drove last year a yamaha TTR250 from kolkatta to belgium with high altitudes passings at nepal, india, the karakorum highway and armenia. dont have much advice for you but i can tell you that the 250's have there altitudeproblem already once over 2500 meters. for sure. i could arrange the carburator but it didnt always help. its a ****ing haslle and dangerous too. i like 250 travelling. i am now in southeast asia touring around on a 250 but i would do this trip (india-bel) never again on a 250. take something stronger but same style. at least a 400cc. iran has big distances between cities, lost of wind in the dessert and you dont have that problem of the altitude anymore. your better of with another bike.

greetz
niels