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hesitation on the low end

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Howdy,

Looking for some help. xr400 gordon mods year 2004. jets 160,, 60. Riding elevation 8000' 10000'.I also dropped a tooth on my front sprocket. At low rpms my bike hesitates. I mean when I am trying to crawl over rocks on a tight trail in the mountians when i need my power to be smooth. My bike will spit a few times until I get going a little faster. After I reach a certian rpm she runs great. I need it way down low. The people I bought the jets from told my what to put in. Some one also noticed that my pipe was kinda black on the end. No doubt I am running rich i think but how far should i drop my jets and should i drop main and secondary.

THANKS FOR YOUR SUPPORT

STEVE

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Steve ,

have a look at the pilot jet and its adjustment

then look at the needle jet,

the pilot jet does affect the 1/8 to 1/4 throttle range,

to get a better understanding of carburation ,

have a look at this link on carburation

its basic but well explained .

stu

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I agree that it is a pilot jet problem. I would also think that the main might be too big as well because you are riding at 10k ft. I run those same jets and I am at 4k ft. I would check you plug. I am guessing that it is covered in soot. If it is light tan, great. If it is black. try to keep going down two main jet sizes until you get a nice tan color.

Just my 2 cents.

Justin

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same bike, mods & elevation.

i use a 150/52. it rips no bogs!

here's some starting numbers:

0000 ft > 160 / 60

1600 ft > 158 / 58

3200 ft > 155 / 55

5000 ft > 152 / 55 (54 act., turn pilot in more)

6500 ft > 150 / 52 (53 act., turn pilot out more)

9800 ft > 148 / 50

this also helps: http://www.koubalink.com/fuelscrew.html

the klr650 is the one we use. helps to make pilot changes when i change alot of elevation. i use it all the time!

bill

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I'm a new XR owner, too, and learning about all the same things you are. My bike stock had ultra-lean California jetting at 138/42. From what I understand, the hesitation is due to the overall carb design - stock, my bike had it pretty bad if I hit the throttle from idle. I ride from a few hundred ft. above sea level to about 6,000. So, a couple of weeks ago I rejetted to a 155/55 combo, Uni filter, holes drilled in exhaust. This seemed to be a good midpoint for jetting given the range I ride in and at 6,000 it ran great with zero tuning and less hesitation problems. Back at a few hundred ft. above sea level, it was obviously rich - turns out the dealer had the pilot screw out 3 1/2 turns with the original jetting! Anyway, based on what I know, I think these other guys are right, sounds like you are too rich on both jets.

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I agree, way too rich on both jets. When I ride 8000-10,000ft. I run 150/50 and the needle clip at 2nd from top with the Gordon mods. Don't be afraid to drop the needle, it will make all the difference at altitude.

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Did you tell the people you bought the jets from what altitude you are riding at (to be fair, they should have asked). As others have pointed out, you have essentially sea level jetting, so no wonder it runs like crap up in the clouds!

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Thanks for your help.. I put in a 150,,,52 and not only does it run better but there was a very very noticable difference in horse power gain.. Yes the people at the honda shop know the elevation and were I ride but they are the worst machanics and uninformed buch of people I ever met. But I am very happy with my bike now. Much horsepower gain with gordon mods and proper jetting.. :cry:

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