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JD Kit Jetting Advice

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I just bought a JD jetting kit. It is in the mail, so I haven't looked at the instructions yet. Just trying to prepare.


Before I start digging around in my bike and changing the jet, I'd like to know what I need to be doing to the stock also. Some seem to cut the filter and some seem to buy a new filter.

I don't want to have to go through this jetting exercise to find I need to add more things to it for it to work as it should. Hopefully it works out of the box with a few tweaks.


If any of you have installed a JD to your 250X, please could you share your experiences as I'm looking for your help to make this as painless as possible.


I will not be getting a new pipe just yet, so hopefully this can be done without that.


I'm in CO at 5200 feet and will be riding at this altitude and up.


Thanks very much

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 All the jets and the needle can be changed by loosening the band clamps, getting some slack in the cables, and twisting the carb. 


 Do remove the snorkel off the top of the air box and either cut the box top or poke some holes in it with a hot pipe (I used a 1" heated with a propane torch).


 You will need to re-jet again of course when you get the pipe.



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 Do remove the snorkel off the top of the air box and either cut the box top or poke some holes in it with a hot pipe (I used a 1" heated with a propane torch).


Thanks Jim - how many holes at 1" ?  Those are some large holes.

Would you be able to take a pic of this of yours?

Did you get noticeable difference?


For some reason I get some bog in low gears, unless I keep RPM up. I'm hoping the kit will eliminate this, as I have read.

Thanks again!

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I cut the air box, drilled the stock silencer, used the stock air filter, took the cage out of it. To change the carb needle, take the tank and seat off. Remove the top engine mounts. It will make access for changing the needle way easier. I didn't have a bog before the kit and I don't have one post jd kit installation. Went down one tooth in the front sprocket. It is a fun woods bike now. Front wheel comes up with a twist of the throttle. My low end has lots of pull.. I did not cut the pink wire.

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I got six or eight holes in the top (don't remember off-hand).

The ccc (closed course competition ) bulletin from Honda suggets cutting off the top and part of the sides. I didn't want to go that far as I often get in water up to the tank plus I kept the stock exhaust

You may want to cut the entire top with getting an after market exhaust (and that should be plenty)

Can't say how much of a diff that made alone as I did it with the JD kit

Totally different bike now. Their jetted so lean from the factory. your in for a real treat if your stock. will run cooler too.

I also dropped a tooth on the front, But that's a tad too much for me. Next chain and sprocket change, I'm going back to a 14 front and will pick up a few on the rear (changing the front sprocket one down is easy as it doesn't change the chain length)


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Several ways to improve the X so + 1 on the previous posts;


There are some links in the sticky for jetting plus Rick Ramsey's web site, but most of the jetting will be very close to what JD recommends so I think that is a good starting point.


My mods are similar to Jims, just two rows of holes in the top of the air box, diameter to fit between the center rib and the sides, no screen, a Uni filter, plus remove the snorkle,  I also have three vent holes in the right side of the air box. And a Yosh TEC exhaust system. The air box mods seem to have the biggest impact on jetting.


The 13 tooth sprocket makes my bike a bit too sensitive, for me,  to throttle in first gear when riding technical so I use second and slip the clutch (the clutch is that good, almost like my Trials bike). Next ride will be back to stock 14.


The JD kit will have two needles, a 42 pilot, a bunch of main jets, and two different O rings to mod the accelerator pump linkage.


I would also check the accelerator pump squirt with the carb on the bike,

Since the carb is so difficult to remove I suggest doing a thorough check out when it is off the bike.  I use a bread baking pan for cleaning the carb and a cooky sheet to keep all of the parts together. Be careful of the little O ring and washer above the mixture screw spring, the washer is between the spring and O ring.  

Make sure you can get good carb cleaner flow out of the three discharge ports in the throat.  One above the mixture screw, one above the pilot jet, and the AP squirter.  If plugged you'll probably need to back squirt cleaner from throat to clear them. 

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So I jetted with JD kit and I'm really happy. Bike is definitely more responsive and snappier.

The kit install was okay. Could have been easier, but I would do it in half the time now that I know how. Some lessons:

  1. Get a long Allen wrench for the top of the carb. You can buy those Allen wrenches that allow you to turn at an angle. Hope you have a friend with small fingers.
  2. The needle comes out easily. Twist throttle. You will need a long wrench to remove needle nut.
  3. Getting the jet out was a pain in the a$$. Fortunately a neighbor had a wrench with link that helped get in there.
  4. The pilot jet wasn't too bad. Used the wrench with a flat for this too.

It took about 4 hours with some groaning and moaning. I could do it in about 90 minutes again. I'm not a grease guy. Perhaps it would have taken less if I didnt have a few beer breaks.

I also installed the fuel screw - this was done a few days later. I was surprised at how you could get the stock fuel nipple out with a blue plastic electrical connector. The fuel screw I change as the bike warms up - it is not set it and forget it...

The guys at JD are awesome. I called them and they were happy to talk to me and go through everything. I wish the airlines offered the service that JD does. I wish that JD sells other things.


The bike had some starting issues after the fuel screw install. After another call with JD and some playing around, I can start the bike with one push of the button. The bike is fine tuned like my wife, so little adjustments are needed depending on the the environment. I let the bike get warm then turn the fuel screw out 1/2 a turn and it purrs... no pun intended.

I also cut the air box. I used a heated knife and it was quite painless apart from the burning plastic fumes.


The kit really wakes the bike up.

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Here's my story . . .


Skip down to where I did the JD kit.


I cut the top off my air box.  You'll have to raise the rear end(lower the sub frame).  Sounds hard, but it's no big deal, takes about 15min.  I also unbolted the rear shock for some extra space.  Remove the airbox from the bike and do the job.  I recommend a Weller Solder gun.  It's a great tool to have if you don't have one yet.  It's cuts the box like butter.  After you're done, put the box into a bucket of hot/soapy and clean it up like new.  I used dishwasher power.  I keep it on hand for cleaning my air filters(notoil).  (do your valve measure and plug maintenance while you're hear.)


Install the JD kit.  Just follow the instructions.  To remove the main jet, I used a socket cap.  A socket wrench will not fit in the space under the carb.  It basically provides your socket a hex head so you can get a wrench onto it.   A long set of tweezers is a plus when doing the needle.

If you don't have one, buy a Craftsman Socket Cap set like this one:



I drilled a few small holes into my baffle.

I removed the air filter screen.

I installed the smog tube removal kit.

My carb already had a twist tie on the accelerator pump linkage.

I installed a remote fuel screw.  This is a must have!


This stuff seems intimidating, but it's not brain surgery.  You just need to take your time and read the manual.  If you get tired, take a brake or finish it the next day.  Don't be put off by guys who say they did things in "20 minutes".  It'll take as long as it takes, but it will get done and you'll $ave!  I always say, if you're doing things right, these bikes are 2 hours in the shop for every hour in the woods.  If you don't have tools, BUY THEM.  Things are cheaper than dirt these days, so there's no reason not to have the correct socket or wrench etc.  You're saving tons on labor, so don't be cheap.


The bike runs great.  Not noticeably louder, but way more peppy and "happy".


Edited by tomjv

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