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Drank the Kool Aid - Airbox opened, JD kit and now won't idle. Suggestions?

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So I couldn't resist and drank the Kool aid so to speak. I was nervous about changing a bike that ran good but everyone's talk about how much better they run uncorked and jetted got to me so I did it. Here's what I did to my completely stock 2007 250x:

1) removed smog pump (AP block off kit)

2) 4X4 air box opening

3) removed backfire screen added twin air filter

4) drilled exhaust baffle

5) jd kit red needle 4th clip (tried 3rd too), 155 main

6) R&D Flex Jet fuel screw

I live in Utah at about 4500', temps 70 at night up to 100 during the day and ride from home up to 10000'. I asked JD when I got the stuff and they said 155 main when it's hot, red needle 3rd clip.

So, I got everything done, put her back together and she won't idle. What's odd, to me at least, is that fuel screw and idle screw adjustments don't seem to make any difference. If I hold the throttle just open she runs great, response is great and riding it around the block it kinda scaried me it lifted the front wheel so easily,but it won't idle. No popping on decel either.

Idle is controlled by the pilot jet rand fuel screw to an extent right? I put the new JD 42 pilot in even though the stock 42 was running fine but I'm wondering if possibly she is running lean at idle? But it won't idle under choke either. Any way to test this? Buy a 45 pilot?

Any suggestions on what to do or how to diagnose? I have read others settings here and at crfsonly but to no avail.

Much appreciated.

-aktex

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Che

So, I got everything done, put her back together and she won't idle.

Any suggestions on what to do or how to diagnose? I have read others settings here and at crfsonly but to no avail.

1. Check the band clamps on the rubber boots between the engine and the carb. Make sure everything is fully seated and their tight. If you have an air leak, this will lean you out.

2. Check the hot start plunger. make sure it's moving and it's fully screwed into the carb. If not, this will lean you out.

3. It's easy to put in the slide upside down; did you have it out? If not, move on. If you did, check that it's installed properly and that the seal on the backside is not damaged.

4. You got gunk in the carb when it was open and the pilot circuit is now plugged or the JD jet was plugged.

5. Make sure your fuel screw is still in.

The JD 42 is no different then the 42 you had in there. I'm still running a 42 and the bike should idle with that with the mods you've made.

Jim.

BTW, "drinking the kool aid" means switching to a KTM.

Edited by JimDettman

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Alright. I checked all those things, cleaned the pilot and same thing. Now get this...it will idle with the hot start lever pulled. As soon as I let that out it dies. I'm lost. That makes me think it's somehow running rich. Could I have installed the fuel screw wrong or something? Oh boy.

Thanks for your help guys.

That's funny that "drinking the kool aid" means that in the dirt bike vernacular.

-troy

Che

1. Check the band clamps on the rubber boots between the engine and the carb. Make sure everything is fully seated and their tight. If you have an air leak, this will lean you out.

2. Check the hot start plunger. make sure it's moving and it's fully screwed into the carb. If not, this will lean you out.

3. It's easy to put in the slide upside down; did you have it out? If not, move on. If you did, check that it's installed properly and that the seal on the backside is not damaged.

4. You got gunk in the carb when it was open and the pilot circuit is now plugged or the JD jet was plugged.

5. Make sure your fuel screw is still in.

The JD 42 is no different then the 42 you had in there. I'm still running a 42 and the bike should idle with that with the mods you've made.

Jim.

BTW, "drinking the kool aid" means switching to a KTM.

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Troy,

So you have the opposite of the usual problem, which means that possibly the air passage for the slow circuit is plugged. That runs from the end of the carb where the air box mounts forward towards the engine. Depending on year and model, you may actually have a jet in there. Looking from the end of the carb through the venturi on the air box side, it would be the passage in the 7 o'clock position (there are two, the other is at the 6 O'clock position.

Run a piece of fishing line through it with the slow jet and pilot screw removed and use some carb or brake cleaner (be carefull if you use carb cleaner, it melts plastic and rubber, but it also disolves gas varnish, where brake cleaner won't as easily)

The other thing could be that even with a 42, your too rich for your altitude. I wouldn't think so, but I would check the jetting sticky at the top of the forum for others setup and look for one that's the same altitude you are. If their using a 42, then the air passage is plugged.

The hot lever does exactly what you said; it leans things out by introducing more air into the carb.

Jim.

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Got it worked out. No idea what I was doing wrong. I took the pilot and air jets out and cleaned em, made sure the boots were seated and clamped and fuel screw was installed properly and she's back in business! Now just need to adjust the fuel screw a little and she should be good to go.

Thanks for the advice Jim I really appreciate it!

-troy

Edited by aktexican

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I still need to fine tune the fuel screw and I have only ridden around the block a few times so far but I would say it is maybe worth it. Definitely more power but not heaps. Throttle response is improved for sure. I have changed the rear sprocket to a 48t so I can ride at a reasonable speed on the roads between and to/from trails which sacrificed some low-end torque. These mods seem to have made it up for it some. I can lift the front really easily in the first few gears.

The other thing I am curious/worried about is a big loss in fuel economy. I was getting really, really good range before.

I'll report back after I get some real trail miles in on her.

-troy

How does it run compared to before the mods? Was it worth while?

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I still need to fine tune the fuel screw and I have only ridden around the block a few times so far but I would say it is maybe worth it. Definitely more power but not heaps. Throttle response is improved for sure. I have changed the rear sprocket to a 48t so I can ride at a reasonable speed on the roads between and to/from trails which sacrificed some low-end torque. These mods seem to have made it up for it some. I can lift the front really easily in the first few gears.

The other thing I am curious/worried about is a big loss in fuel economy. I was getting really, really good range before.

I'll report back after I get some real trail miles in on her.

-troy

Alright, I have gotten in a few rides and mostly have the fuel screw adjusted just about right. I did one of my usual loops yesterday and gas mileage seems about the same. I burned a touch more but mostly because it's a little more fun to twist the throttle now.

So, I can't speak for other model years but for a 2007 I would say the jet kit, fuel screw, airbox and baffle mod are worth the time/money. It isn't a huge difference (say 5-10% tops) but it is there. Response is better, pulls from low rpms better and overall seems snappier. My bike ran really good before and honestly if you are just trail riding and are content with performance I would say don't do a thing. However, if you are curious, like to tinker like me and want to really dial things in then by all means go for it.

Cheers,

-troy

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Alright, I have gotten in a few rides and mostly have the fuel screw adjusted just about right. I did one of my usual loops yesterday and gas mileage seems about the same. I burned a touch more but mostly because it's a little more fun to twist the throttle now.

So, I can't speak for other model years but for a 2007 I would say the jet kit, fuel screw, airbox and baffle mod are worth the time/money. It isn't a huge difference (say 5-10% tops) but it is there. Response is better, pulls from low rpms better and overall seems snappier. My bike ran really good before and honestly if you are just trail riding and are content with performance I would say don't do a thing. However, if you are curious, like to tinker like me and want to really dial things in then by all means go for it.

Cheers,

-troy

I decided to go ahead and do mine. I wanted to get in and do the AP mod, so it kinda made sense to invest the ~$14 for a couple jets. I hope to have it back together today or tomorrow for some testing.

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So, I can't speak for other model years but for a 2007 I would say the jet kit, fuel screw, airbox and baffle mod are worth the time/money. It isn't a huge difference (say 5-10% tops) but it is there. Response is better, pulls from low rpms better and overall seems snappier. My bike ran really good before and honestly if you are just trail riding and are content with performance I would say don't do a thing. However, if you are curious, like to tinker like me and want to really dial things in then by all means go for it.

Cheers,

-troy

I think if you went back to the prior gearing, you might be a little more impressed. I wouldn't hesitate to do this considering the $ spent vs the return. It's probably one of the cheapest things you can do. But even if you didn't get more power, one of the main benefits is that the motor will run a lot cooler now, which at first is not at all obvious.

Jim.

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I think if you went back to the prior gearing, you might be a little more impressed. I wouldn't hesitate to do this considering the $ spent vs the return. It's probably one of the cheapest things you can do. But even if you didn't get more power, one of the main benefits is that the motor will run a lot cooler now, which at first is not at all obvious.

Jim.

Jim,

thanks for the follow up. That was one of the reasons I did the mods. Basically to get the motor running the way everyone says it should...cooler and richer. Funny you should mention the gearing, I put a 13T on the front (now running 13X48) which is very close to stock but haven't taken her out yet. I will get a chance in the next day or two and report back.

thanks again,

-troy

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