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250 X off idle responce compared to a KDX200.

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I have a completely stock 2004 250X. I run new 93 octane gas. I am trying improve throttle responce / control. From new the bike will not idle. It came with the fuel screw two turns out. It also would not respond to very small throttle openings. It would just surge and spit until the throttle was opened more then it would take off hard and run clean up to full rpm. I have been opening the fuel screw 1/2 turn at a time and running the bike. At 3 1/2 turns the bike started to idle and the off idle throttle control got better. I kept going out with the fuel screw and I am now at 5 full turns. At this point the responce is even better but not good and the bike starts to show signs of being to rich ( a little black smoke comming off idle ) I have a kdx200 and I ride them back to back as a test. I am not sure what to expect with the 250X. With my kdx I can putt around my yard or up hills at idle and any speed I want above idle up to full rpm in any gear within the power limit of the bike. With the 250X I can putt around at idle or at say 2000 rpms above idle but it will not run at rpms just off idle. When I try the bike does not respond to very small throttle openings it just kind of gets weird and then it takes off when it gets a little more throttle and runs fine at like I said 2000 or so rpms above idle. If I am in a rocky slipprey area this is a real problem as the bike will want to die then spin. I went throught this long explination because I have very little four stroke experience and I want to make sure you guys understand whats going on. The bike is completely stock. I ride at 100 to 2500 feet it is about 45 degrees and I make sure the bike is very warm before I do any changes. I am not very fast and the bike has plenty of power stock I just want to get the best throttle control / responce I can. The bike is real work compaired to the KDX at low speed. At any other speed it is better.

I would like to know the following

Can I hope for smooth of idle responce?

If so what settings.

How far out can I go with the fuel screw?

What pilot?

What main?

needle clip slot ( from top or bottom )?

Turns on fuel screw?

Leak size?

Anything else that would help.

Please help.

Thanks.

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First off, the X is insanely lean stock, especially for your altitude and temperature.

Fuel screw/pilot jet: we went from the stock 40 to a 42. General rule of thumb on the fuel screw is a range of 1 to 3 turns out: less than 1 and you need a leaner pilot, more than 3 and you need a richer pilot. Ours is set a 2 turns out.

Needle: we went 2 clip positions richer (lower) from stock. Response was improved markedly.

Main: we went from the 130 to a 150. Pull was improved markedly.

Leak jet: went to a 55; did this before any of the other changes and didn't notice much difference, which lends credence to the belief that the other jetting must be nailed down before a leak jet change will yield positive results.

The bike is completely stock motor-wise, no changes to exhaust or airbox. Response, pull and overall performance is much-improved over stock. We are at ~1000' and temps have ranged from 75 to 95. As much of a pain as it is to get at the carb I'm hoping we don't have to go even richer as the temps go down.

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Thanks, I already purchased the 42 pilot and the 150 main.

Did you remove the Carb to do this?

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Did you remove the Carb to do this?

Not completely, just pulled it out of the air boot and intake manifold ... after what seemed like an almost complete disassembly of the bike 😢 . I'd very much recommend moving the clip (at least one position) as I think that had the most effect on things. It will come into play much more than the main with the problem you're describing. You could even give that a try before the other changes to see if it helps.

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When I got my 250X (a CA model) it was lean, but ran MUCH better than you describe with yours. I think you should try some jetting changes of course, but something's not right for the bike to run THAT poorly. When I rejetted mine I went ahead and pulled the carb off just to have look at it and get familiar. Perhaps you should do the same and look it over thoroughly for blockages or other problems. Of course if your going to re-jet, and you should, you may cure a blocked/damaged jet right there.

I started off on my jetting with:

42 pilot

Fuel screw between 1 3/4 and 2 1/2

Needle raised 2 positions

135 main

I need a 55 leak jet so I can try that, I'm thinking of trying the stock "R" needle or 49 state "X" needle, and I'll keep stepping up the main until I get what I want. It runs good, but I feel I can get a bit more snap off the bottom still.

I ride mostly at 1500 up to 6000, from 100 deg to the 30's so I don't want to get to rich, and I have to be able to make adjustment now and again. I'm still playing with it as I only have about ten hours on the bike too. I have cut the airbox out where the snorkle is and removed the little rubber cover. I also cut off the inner end of the exhaust diffuser which only makes the bike very slightly louder.

Make no mistake though, something's not right for the bike to be running as poorly as you describe.

I also modified my fuel screw to make trailside adjustment easy.

CRFfuelscrew.jpg

Good luck with it, if you're familiar with jetting a two stroke you can jet the CRF too.

Doug

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If I go in to just move the needle I will still have to do most of the dis-assemble right?

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No, you can just pop the seat/tank off and go in through the top of the carb. You should have got a little tool with the bike for this. It's basically a piece of wire with a small chunk of hose on the end that will slip over the top of the needle so you can lift it out. If you didn't get it you can make something.

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O.K. thanks again. Just two more question. I hear lots of people on this forum talking about valve problems. Do you think going to a larger main would keep the bike cooler and maybe help the velve problem. I know that raising the needle will also richen things up. And, will the bike ever run as smooth down low as a nicely setup KDX?

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I just picked up a X. It so-so...but I put in a 42 pilot, needle from the Crf250R and a 152 main, set the screw at 2.5.

It runs really well from idle(which you may want to turn up a little)but is too rich on top

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There could be some validity to the richer bike/better valve life theory, but unless the bike is so lean that it's running quite hot I wouldn't put much stock in it. I've been gone for about a month but just checked the valves on mine before I left and they were spot on with about ten hours on the bike.

As far as running smooth, mine will come off idle with prfect smoothness and control all the way to redline. The only issue I have is if it's right off idle and I SNAP the throttle open it will stumble. It's very minor, especially when the engine is at full operating temp. I think I can get rid of most of that and get a bit more juice off the bottom with further jetting refinement.

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