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Jet needle help

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I just picked up a 2008 WR250F. It came with a JD jet kit installed, but none of the spare brass. Unfortunately, the carb has the red needle in it. I ride at lower altitudes and the bike is running too lean, even with the clip all the way down. Is there a needle that's made by Keihin which performs similar to the JD blue? Or might someone have a blue needle they'd be willing to sell or trade for a red?

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an OEM YZ250f needle is what I'd suggest . Get one from the last year  ( '13? ) of the carb'd bikes and you'll be set.  Clip 2-3 will work for you and 2 works best for me but that will depend on any other mods your bike may have .  btw, the stock YZf needles are under $10 !   good luck

 

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Thanks for the advice. I should have mentioned, the bike has snorkel removed & FMF Q4 silencer. Is the OEM needle still the way to go?

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9 hours ago, rwphoto said:

Thanks for the advice. I should have mentioned, the bike has snorkel removed & FMF Q4 silencer. Is the OEM needle still the way to go?

that's what I'd do without hesitation.  My snorkel is removed and grey wire cut . Stock muffler .   I'm also running a 45 pilot, 178 main and 55 leak jet . It runs perfect and I couldn't be happier !

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Agreed, the newer YZF needles are good stuff.  "Newer" meaning 2008 and newer.  I had an 09 needle in my WR250F and it was spot on perfect jetting.

Also, be sure to order the YZF needle jet to go with these newer YZF needles.  (the part which the needle slides into & out of).   Sometime around 07 or 08, the YZF's carb got a different needle jet than the WRF.   The YZF needle jet is very little bit slightly smaller and it's not easy to tell the difference.  So, if you buy the newer needle be sure to mark it somehow so you can tell it apart from your stock jet needle.

JD parts were a much bigger bang for the buck back many years ago, back when the YZFs came with poor design needles.   

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Thanks guys! With this info, I should be able to clean up that lean condition at 1/8 throttle.

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That 1/8th throttle issue is probably from the air cut valve (or called coast enrichener valve, or other things).   This device functions to enrichen the fuel mixture at closed throttle when the engine is at higher engine revs, eliminating the "back popping" which is common to the YZFs when their fuel screw is correctly adjusted.  (just a bit of back pop is correct FS adjustment)  From a trail user standpoint, having your bike back-pop causes additional noise, hence the WRs (and CRFX etc) have this circuit on their FCR carbs.  But, the downside, is that the ACV mucks up your jetting at 1/8th throttle with the engine turning some revs.  Your engine gets caught into being too rich and correct. 

Some peeps will argue the ACV doesn't matter and you should leave it alone, yadda yadda, but those folks have not ridden a WR with ACV back to back with a YZF.  Or if they did, ther rode a YZF with incorrect jetting. 

This ACV  circuit can be removed (blocked off) on the WR's carb with a couple of different approaches.  Do an advanced search of these forums with my user name and you'll find where I describe how to block it off.  Be sure to get an air jet (on the air box side of the carb) from a YZF.   Search for air cut valve, user name BazookaJoe 

 

Hope this all helps.

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Thanks for that excellent info!

I'll try to describe the issues I'm trying to cure in more detail, hoping you can tell me if it still sounds like the problem you just described...

When I hold the throttle open about 1/8 turn in free rev the blubbers and the RPMs fluctuate. When riding at a steady 1/8 throttle, the bike felt like it was suffering from a lean condition, causing it to surge. I knew it had that red needle in it, so I tried pulling it up one notch at a time. By the time I got it up to the 5th notch, the problem was lessened, but not fully cured. That's what led me to guess it needed a needle that was richer at partial throttle. 

Also, and I understand this could be a separate issue, snapping the throttle open from idle produces a bog. If the throttle is snapped fully open, it will kill the engine. I'm running a 42 pilot, 65 leak, and 2 0-rings on the accelerator pump linkage. I've take the carb off the bike and verified that the pump is working. It squirts for about a 1.5 second duration.

Edited by rwphoto

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You might want to try a smaller number leak jet.  Try a #50 or so, but the difference won't be huge.  BTW, If I recall correctly, the Honda jets are less expensive and you can get the Honda part number from one of those CRF150R (the racer model).

Your bike's blubber description sounds pretty much what those bikes run like when the pilot & needle aren't correct, and also this can be the effects from that hateful ACV.  And another thing too, is sometimes the problem is from the pilot jet.  Even thought the PJ might look all nice and clean, there is debris inside.  It doesn't take much to change the jet's flow because it's such a small orifice.

Also, search via my username for some tips on how to pull the pilot jet from the carb with the carb still on the bike.   

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Thanks to all for your advice. I dropped in an NFPN needle with the clip on the 3rd notch and the bike is running sweet. I was happily surprised to see such a simple change take care of that lean surge at steady 1/8 throttle. 

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