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JD Jet kit and YZ250F???

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I finally got to test my JD kit at elevation today in Colorado. We were riding at around 9000ft on average and 70 degrees and the bike actually ran horrible. 2003 YZ250F stock except vortex X-10 ignition and a Pro Circuit type 496 slip on exhaust. James w/JD suggested stock pilot, AS 1 ¾ turns out, 175 main, and red needle in the No.4 position. The bike barely would take off from a stop without getting up high in the rpms and slowly slipping out the clutch, Then while riding, if you were in a higher gear and tried to just ride, the motor would start cracking and popping and sputtering like it was running out of fuel(towards the end of the day I thought I was out of fuel but I was wrong) and totally GUTLESS. Going up hills was even worse. CRACK,POP Sputter, until I would hit a lower gear and twist the throttle almost wide open or start slipping the clutch excessively and roll on the throttle to ¾ or full throttle and it would then pick up power. Other than that, The bike was pure gutless pig. Worse than it has EVER been since new. Any help will be GREATLY appreciated. I know the kit will work, I just need to know where to start adjusting.

OWENLO :thumbsup:

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Jetting is an art and one can only give you a starting point. It's tough to diagnose your bike when someone is X # of hundred miles away. Burned, James D, and many others are very knowledgeable guys but they are not test driving your bike either. They can't hear the exhaust note, or feel how the power builds or doesn't build.

Check for an air boot leak, make sure your filter is clean and not over oiled, if you had the carb apart did you put everything back together, when you say 4th clip did you count down from the top?

Read this post, there is some great information there. I'm still dialin both my bikes in. The more I read, the more I learn, the more accurately i'm getting my bike dialed in.

Here is the post link:

http://www.thumpertalk.com/forum/showthread.php?p=3671956#post3671956

Also head over to http://www.thumperfaq.com/jetting.htm

and read the article on jetting the carb, and while you are at it read the posts at the bottom of the page on what a bog is, how lean is too lean, and the many other posts this will help alot.

The biggest thing is to set the mainjet first. PERIOD. Don't worry about how the bike runs below 3/4 throttle. When you have the correct MJ installed everyother bit of tuning will go alot smoother.

Then set your needle clip position, then set your FS (after your bike is fully warmed up for about 10 mins), then time your AP, and adjust your leakjet size for the amount of "hit" you prefer.

Make yourself a notepad jetting document of information on your pc. Copy and paste the good stuff into notepad for future reference, and keep a section of jetting results with weather temps and altitudes at the top of the notepad. The good settings where your bike ran well and the bad settings where it didn't.

Be cool, jetting can be frustrating and seldom on the first try does the bike run great.

Greg

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Use the next higher elevation setting. The kit describes 6000-9000ft and 9000ft and above. The next higher elevation setting suggests using a #170 main jet and leaner clip position.

Also, try turning the fuel screw inwards. As the instructions describe, "the fuel screw may need to be adjusted", and results differ between bikes.

Estimate-

Stock pilot jet

1 1/4 turns out

Red #3 from top

#170 main jet

Even with the best possible jetting, the 250F will have much less power due to lack of air at high elevations.

Thanks,

James

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This is the jetting I run I live at 7000 ft and it is a short ride to above 9000ft the only different is I am running a 48 pilot the bike runs good a pulls strong.

Use the next higher elevation setting. The kit describes 6000-9000ft and 9000ft and above. The next higher elevation setting suggests using a #170 main jet and leaner clip position.

Also, try turning the fuel screw inwards. As the instructions describe, "the fuel screw may need to be adjusted", and results differ between bikes.

Estimate-

Stock pilot jet

1 1/4 turns out

Red #3 from top

#170 main jet

Even with the best possible jetting, the 250F will have much less power due to lack of air at high elevations.

Thanks,

James

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Thanks all,

I will give this a try. It has been difficult to really narrow this whole thing down as I have been riding at different elevations averytime I have ridden and haven't gotten anywhere close yet. As soon as I nail down one elevation It wont be any problem staying dialed in and adjusting for elevation.

Thanks again,

OWENLO :thumbsup:

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Just to inform everyone, I goofed on James's suggestions for my jetting. He made me a recomendation for 5000 to 8000 ft. and I took off at 9000+ ft. So I am 100% confident that if I get my head out of my :thumbsup: , That James will have me dialed in in no time. Thanks all. :ride:

OWENLO :applause:

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