Jd Jetting Q's for yz 426


5 replies to this topic
  • yamaha908h

Posted June 13, 2008 - 11:34 AM

#1

I have an 01 yz426. I got it over the winter and I have to say Its a great bike except for the bog. I just got my JD Jetting kit in the mail and need some recommendations or a good baseline. My bike has a power now valve, full FMF exhaust, and a twin air filter. My first 4 stroke so I have no clue where to even begin with the kit. My elevation is 1120 feet and temp is 80-95 degrees, humidity is 70-90%. Carb is stock now. I want the bog to go away for sure. I also have a quickshot 1 ap cover. Are those worth installing? Any help would be great because im clueless about this bike and just want to learn from the 426 gurus. Thanks in advance.:thumbsup:

  • BASSic

Posted June 13, 2008 - 09:05 PM

#2

I have an 01 yz426. I got it over the winter and I have to say Its a great bike except for the bog. I just got my JD Jetting kit in the mail and need some recommendations or a good baseline. My bike has a power now valve, full FMF exhaust, and a twin air filter. My first 4 stroke so I have no clue where to even begin with the kit. My elevation is 1120 feet and temp is 80-95 degrees, humidity is 70-90%. Carb is stock now. I want the bog to go away for sure. I also have a quickshot 1 ap cover. Are those worth installing? Any help would be great because im clueless about this bike and just want to learn from the 426 gurus. Thanks in advance.:thumbsup:


When you get your JD kit, it comes with two needles and a few main jets. For the YZ426, it comes with a 160, 165, 168, and 170. Stock is 162. It also comes with all the instructions for which settings you should use at your temperature and altitude. Keep in mind it's just a baseline and you may need some more tweaking.

For me (0-1000 feet elevation) it said to go with the blue needle, 4th clip, and a 170 main jet. The 170 main worked great when it was 40 degrees outside, but in the warmer weather it was way too rich for me so I went down to a 165. I last rode my bike a week ago when it was 100 degrees and 80% humidity and something didn't feel right. Low-end power was great, but from 1/2 to full throttle, it wasn't as strong as it usually is.

I can't find the original instructions that came with the kit, but I'm wondering if I should be switching to the red needle when it's this hot and humid and maybe raise the clip one position.

  • whyzee426F

Posted June 13, 2008 - 09:27 PM

#3

I have an 01 yz426. I got it over the winter and I have to say Its a great bike except for the bog. I just got my JD Jetting kit in the mail and need some recommendations or a good baseline. My bike has a power now valve, full FMF exhaust, and a twin air filter. My first 4 stroke so I have no clue where to even begin with the kit. My elevation is 1120 feet and temp is 80-95 degrees, humidity is 70-90%. Carb is stock now. I want the bog to go away for sure. I also have a quickshot 1 ap cover. Are those worth installing? Any help would be great because im clueless about this bike and just want to learn from the 426 gurus. Thanks in advance.:thumbsup:


My opinion: the power now and the quickshot are a waste of your time and money, but you'll find lots of folks run them anyway. I say this because I spent some time researching to conclude there is no scientific evidence (dyno results) that prove benefit of either. Only evidence seems to be seat-of-the-pants o-meter.

Follow the instructions that came with the jet kit, ensure your carb, filter, and plug is clean and plug properly gapped. Jet kit instructions should put you at the 90% solution, then run it and watch the plug for the rest.

One question for you...do you get the bog while riding or only while cracking the throttle with the bike sitting still? I ask because I can crack throttle wide open on mine and bog it while the motor is free spinning, but have no issues while riding, so I've opted to leave mine alone. Hill climbs aren't even an issue for me and I'm at 2500 ft with stock jetting, stock exhaust, aftermarket filter, so again, I left it alone...especially since it'll outrun just about anything out here on the desert floor...having run across dry lake beds against CR450 and KTM 525 (pulls away due to 6th gear).

I suggest you get a manual so you can see carb breakdown. Highly recommend cleanable stainless steel (micronic) oil filter because factory ones are crap/don't filter out enough; run synthetic oil, and change it every 10 hours. Cam chain needs changed at about about 75 hours (I think factory manual says 50) depending on how hard you ride.

I hope it works out well for you. Welcome aboard.

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  • Birdy426

Posted June 14, 2008 - 03:09 AM

#4

Yup, the recommendations in the JD kit worked spot on for me as well. Try what he recommends and it should be just minor tweaks from there. As far as a bog, I never really had one on my WR (YZ timed or with hot cams, and YZ pipe), but many folks on the board here swear by the BK mod to adjust accel pump "squirt" duration, and by the O-Ring mod. I think the newer JD kits even come with the O-Ring. If not, search for "O-Ring Mod" and you should find plenty of instruction.

The Quick Shot really did nothing for me. As far as the powerNOW, I agree that it likely doesn't add anything you can detect onthe dyno, but it did make starting easier, and feels a bit crisper at lower throttle settings.

  • yamaha908h

Posted June 14, 2008 - 04:16 AM

#5

Thanks for the help guys! I didnt state that the bog was happening during a quick burst of throttle. It was tolerable in the begining but after I put the exhuast on it the bog is much worse. It does it when I jump(not good) and coming out of corners. The quick shot came with the bike not installed. the past owner tried and said it didnt run right with it in. Sounds like somthing for ebay. Yes the JD Kit came with o rings in it. The last bike I had was a 99 YZ 250. I loved it but had a Bad wreck and sold it. Semi retired for 5 years and found this bike for 1400$ and couldnt pass on it. Also what plug is recommended so I can pick up a couple. Thanks again

  • Birdy426

Posted June 14, 2008 - 01:20 PM

#6

Plug is a CR8E in NGK...not sure about other brands. If you already have the quick shot, I would say put it on when you install the JD kit...what have you got to lose? Plus, now that the QS2 is out and the retail price for a Quick Shot is down around 50 bucks, you probably won't get much for it on Flea Bay anyway.





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