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Re-Jetting the YZ250F

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I have searched the site but really not finding what I need. I have a 2004 YZ250F that I bought used. It has a Big Gun Exhaust system, But still has the stock jets, 182 main, 42 pilot, and 90 leak. I have struggled with clogged Jets and am going to order new. PROBLEM: I believe the bike is running lean according to the plug, and its not wanting to idle, start, and when it does, it Pops, Cracks and just totally sounds like crap. Once riding its a screamer. no popping, no hesitation, and no bogging.. What would you guys suggest for Jetting for this type of Exhaust?

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I have searched the site but really not finding what I need. I have a 2004 YZ250F that I bought used. It has a Big Gun Exhaust system, But still has the stock jets, 182 main, 42 pilot, and 90 leak. I have struggled with clogged Jets and am going to order new. PROBLEM: I believe the bike is running lean according to the plug, and its not wanting to idle, start, and when it does, it Pops, Cracks and just totally sounds like crap. Once riding its a screamer. no popping, no hesitation, and no bogging.. What would you guys suggest for Jetting for this type of Exhaust?

I can't belive those are the stock jets....Main is too big, as is the Leak jet.

I would do 170 main, 45 pilot, 45 leak, NCVS needle.

If it does not idle, you pilot jet or jet passage is clogged. Clean the passage and replace the jet.

Check your Accelerator pump squirt while you are in there.

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Thanks, I'm gonna tear into it again today. Hopefully its just the jet passage. How do you check the accelerator pump?

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Thanks, I'm gonna tear into it again today. Hopefully its just the jet passage. How do you check the accelerator pump?

Lift up the subframe, and with the motor off, whack the throttle and look inside the bell of the carb. You should see the pump nozzle spray a stream of gas right into the head.

The most common issue is a clogged nozzle: you have to carefully spray carb cleaner up from below into an angled passage. Do it with the slide all the way up, cause you DON'T want to get carb cleaner on the slide (or anywhere else if possible). Use spray brake cleaner for general cleaning.

Next most common is a old or dryed out diaphram: replace it.

http://www.dirtrider.com/tech/141_0707_keihin_fcr_carb_rebuild/viewall.html

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Got it back apart and noticed I had placed the side plate on the slide on upside down. I cleaned everything again and put it back together and it runs allot better now. Was still kinda hard to start though. Oh yea, and the pilot jet passage was clogged too. Thanks for that! Fuel screw is out about three full turns, So i guess I need to go up a size on the pilot, Right? its 42 now, 45?

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Lift up the subframe, and with the motor off, whack the throttle and look inside the bell of the carb. You should see the pump nozzle spray a stream of gas right into the head.

The most common issue is a clogged nozzle: you have to carefully spray carb cleaner up from below into an angled passage. Do it with the slide all the way up, cause you DON'T want to get carb cleaner on the slide (or anywhere else if possible). Use spray brake cleaner for general cleaning.

Next most common is a old or dryed out diaphram: replace it.

http://www.dirtrider.com/tech/141_0707_keihin_fcr_carb_rebuild/viewall.html

What if you threw card cleaner all over the carb?

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Yes

You mentioned that one shouldn't do it

Would it be a problem? I did it

My YZ250F 2008 I'm trying to find how to get the right card

I have a main 180, 42#, 1600 mts altitude at the equator, red Jd needle 3rd from top. Bike starts well with choke, the idle remains high and it comes back after some time, I touch the throttle and it again remains some 5/10 sec until it comes back to normal. It runs great and has good power but it pops once I release the trottle and misfires a little

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