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Old 03-07-2014, 05:16 AM   #1
Chiriqui Charlie OP
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Joined: Oct 2011
Location: Panama Highlands
Oddometer: 401
More air for XT250?

My XT runs great from sea level to about 8000 feet, but there is an 11,000 foot pass that I need to cross six or eight times a year, and the bike loses all power making it over the top. Is there any way I can mod it so that I can allow more air when going over the pass, without removing the seat?
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Old 03-08-2014, 06:24 AM   #2
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Joined: Mar 2006
Oddometer: 1,906
Does your XT have a carburetor or fuel injection? If it has a carburetor, going down one size on the main jet might improve your power at high altitude. More air with the same jetting will still give you a mixture that is too rich.
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Old 03-08-2014, 07:01 AM   #3
Chiriqui Charlie OP
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Joined: Oct 2011
Location: Panama Highlands
Oddometer: 401
It is a 2012 with a carb. I was assuming that just giving it more air would help when I go over 9000 feet (I could be wrong, I know very little about engines), and I am hopeing that there is some mod that I could control on the fly without removing the seat. It runs very well at lower altitudes.
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Old 03-08-2014, 07:12 AM   #4
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There really is not much you can do other than split the difference on the carb's jetting so it runs a bit lean at sea level, and still rich at high elevation.

Dunno how hard it is to change the main jet on those, but if it is not a huge bother, you could take a smaller one with you and pop it in when you are in the high country. 2 sizes smaller than stock should help and not be a disaster down the hill as the factory main jets are usually a bit on the rich side anyway. A 250 at elevation is going to spend some time on the main jet...

I had a DRZ400, jetted it to run well at 8,000 feet as that was the elevation the majority of my trail riding was done at. It was a bit lean at 5,000 feet in my driveway, and rich at 12,000, but serviceable from 5 to 12K elevations. Usually it is colder at sky high elevation, which helps reduce the effect of the thin air. If it runs well down the hill and it is a warm day at 12,000 feet, it is not going to be happy. If you did lean it out enough to run well on a warm day at 12K, it will run like crap down the hill. Set it for your most common riding elevation and rock on. That is just the way it is with carbs.
2010 Husaberg FE450 (plated)
2001 Honda CR250 (out of state riding buddy's bike stored in CO for his annual epic ride) fills my need for the occasional 2 stroke hit!
2006 Yamaha FZ1

Duken4evr screwed with this post 03-08-2014 at 07:18 AM
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Old 03-09-2014, 04:43 PM   #5
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Joined: Sep 2008
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check out the xt225-250 site,did not find in the fische the usual air screw so check them out to find out the mod for this,maybe a keintech screw will fit.
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