OBEJ needle, gotta be wrong, '02 YZ426

Hey all, I still can't get my jetting right on my bike. It just flat out runs like crap from idle to quarter throttle. It is rough and choppy.

I'm at 6000ft. I've set it at 158main, 42 pilot, 3rd clip position. I've played with 4th and 3rd positions and 3rd makes it run a little better but still not like it should.

It's a Canada model, so I'm having a tough time getting it right. I'm concluded maybe the needle could be the wrong style for what I need. It's got an OBEJ needle in it. Am I on the right track? Thanks

All needles are OBEJ, its the last number that advises what taper it is. Ex: OBEJP

Idle to 1/4.... try a bigger pilot.

I ride at about 3k-5k feet and I'm running a 168 main, 48 PJ and EJP needle #3 spot. Bike runs great with the mods listed below.

Edit: I might have dropped to a 45 pilot. Cant remember at the moment.

Not all needles are OBEJ, stock 00 was an OBEKR.

Oh yeah.... I remember that blasted POS needle.

I usually dont spout unproven nonsense in the tech forums. Sorry bout' that.

Thanks for the info. I checked and it's a OBEJ - P. I've been reading, what about those NCVQ needles?

I'll play around with the pilot jet some more to see what happens...

The JP needle is what Yamaha used starting with the 01' 426 cause the needle in the 00' was a disaster. It should give you satisfactory results and certainly isnt the problem here. Keep it in the #3 clip.

Yamaha makes all kinds of differnet needles each with a different taper. I wouldn't try a new needle until you diagnose the culprit of this problem first. Try a 45PJ and see if it improves.

How many turns out is the fuel screw?

Pincushion, thanks.... my fuel screw is 1.5 out right now. I've tried it with 1 out and couldn't tell any different.

I just put in a 40PJ (cause I have one) and didn't notice any difference after a few laps. I'll get a 45 and try it...

I took my bike to a shop and had it rejetted in May. (I've only ridden it twice since then because of my new quad) and they got it running pretty nice. BUT, they loosened up my throttle so it was abosolutely floppy loose. I CAN NOT stand it floppy loose, it drives me nuts. So I retightened it back up and ever since then I've had a problem it seems like. But it's not real tight, it's just tighter than it was.

By tight I mean, less play, and firmer, ya know? They had about 1/4 turn of play in the damn thing, and it was so loose, every time I'd hit a bump it'd chop the throttle. So, I'm wondering if maybe I messed it up.

So again, the symptoms are real rough idle-quarter throttle, and it's hard to get it to recover. Like, if I'm going along on the gas, and I let off for a breaker bump, then get back on it, it'll be real rough and try and die unless I give it more throttle and get it out of that spot. Basically, I cannot ride it 1/4 throttle or less or it's too rough to ride.

But there is no bog when I punch it, and it runs great top end, mid range and all. Sorry for the long reply, I'm just trying to describe it in text form. Thanks

Did you tighten the cable at the carb or on the bars? (Is there adjuutment on the bars even? I've never looked). I've only adjusted mine at the carb and I like it tight also. I'll leave about 1/8" of cable slack on the pull cable and about the same for the push cable. It is possible that your cable is too loose/tight and its not opening the slide appropriately.

Also try changing the plug and put some fresh gas in.

I've got a bad habit of trying to fix a problem the hardest way possible. Rather than try a new plug or fresh gas I'll rebuild the carb or something else major.

One last thing..... the AP diaphram tends to squirt too much gas into the carb when you first grab the throttle (yamabog!). There's a fix for it, but if you didn't notice this in the past then its obviously not the problem.

I'm still trying to figure out jetting on these bikes. After 15+ years on 2-strokes I'm having a hard time unlearning what I learned working on them.

Pincushion, I loosened the cable at the carb (there's no adjustment at the bars) and rode it loose and it didn't make a difference.

You know, I went for another moto just now and I guess idle-1/4 throttle isn't really correct. It's really idle-1/8" throttle that it stumbles... which kills my trail riding.

Fresh gas, air filter clean, and brand new spark plug. That was last week, when it wouldn't even start, even with pulling it around our field by a quad.

Problem Solved Guys! It was the throttle cables just like I figured. Aparently I used to not know to adjust them.

I had a lot of slack on the return cable so it was causing the nightmare for 2 years (only about 40hrs on bike)! I took almost all the slack out of the return cable then got my freeplay out of the pull cable, and BAM, works perfect!!

Thanks for the all ideas. :banghead:


Be sure to keep an eye on the cable ends at the carb as they like to frey and eventually break.

Glad to hear you got it solved.

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