YZ Needle ??

My buddy and I did the YZ timing conversion (finally got it right) on his WR250F and it really made quite a difference in my opinion. It is much more rev happy throughout the entire RPM range...SO I am going to do the conversion to my WR426F ASAP but this YZ NEEDLE thing is my real question. People have said this makes as much of a difference as changing the timing - any other opinions on that? If so, is the stock YZ needle the way to go? In the stock clip position? Is this an easy change? I've only replaced main/pilot jets before...the needle is in the top portion of the carb right? Any do's or don'ts to this or is it straight forward? Also I have the stock WR exhaust (baffle removed) right now but I am ordering a WB ProMeg ASAP....Will this mod along with the YZ timing change require a main/pilot jet change? Lot's of questions I know - I just want to get this right the first time because we are headed to the Hatfield/McCoy trails in WV for the LAbor Day weekend and I want to be able to roost my unsuspecting comrades who don't know I'm makeing these little mods - this is a covert operation...shhhhh!!


Making the switch to YZ timing makes more of a difference in terms of pure explosiveness than does putting in a YZ needle...although both on their own right help out quite a bit. I myself prefer to keep the WR timing while using a "YZ needle" (E series needle). If you're anywhere close to sea level, many folks have been following the "Taffy jetting" which is approx:


Do some searches and/or find a Taffy post...his jetting will be there. You'll probably run into the same fiasco as everyone else does regarding your local dealer's parts guys not knowing their asses from their elbows...so be prepared. Not sure where people are getting their EMM needles...but you might be having to call Sudco to order some of this stuff (like the MAJ and the adjustable pilot air jet screw).

Given that, unless you dont mind spending money on jets and playing around with different jetting combo's, I'd wait until you buy/install your new pipe before doing much. I think you'll find that your jetting will need to be changed once you go with your new pipe...but perhaps not.

Hope this helps...


Originally posted by LarryCO:

Not sure where people are getting their EMM needles...

5NL-14916-EM-00 is the PN for an ELM off the 250F fiche, this needle is identical to an EMM except it will be a half clip richer.

An aftermarket exhaust won’t require much different jetting, if at all, than a stock uncorked WR in my experience. Once you unplug/uncork/unstop/uncover or whatever you wanna call losing all that goofy crap Yamaha stuck on the WR you will benefit from YZ jetting. The YZ is delivered with out all of that engine suffocating weirdness…

Hey dangler, I grew up in Fburg. Did you go to high school there? My brother is your age and still lives there. Is the riding any good there now?

Hey Mike,

Yeh I grew up in F'burg as well. I went to Spotsy Co. schools up until high school and then I had to go to James Monroe because we were annexed into the city in the early 80's. You probably remember when all that happened. F'burg sure is growing quick now...pretty much just another DC suburb now. Ridind here is OK but alot of the trails are being posted because idiots go in and leave trash, tear things up, etc. and landowners are getting fed up...I can't really blame them. Luckily I have a buddy (the one with the 250F) who's realtives own some land that connects to some good trails. Other than that we have to head out of town to find places to ride...

My brother and I both went to JM. He now lives on River Road. I hear you about the trash and tearing things up. My brother has to bring in his mailbox every night because drunk rednecks use it for batting practice as they drive by. What's up with that?

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