70s jet question

7 replies to this topic
  • drop

Posted May 08, 2007 - 12:32 PM


I just got a 68s and 70s jet in the mail and I'm thinking I'll put in the 68s first. My question is when is the larger 70s jet appropriate? I'm running a full Jardine exhaust system with UNI filter. 1000 feet and 25 to 90 degrees is the temperature range here.

  • BWB63

Posted May 08, 2007 - 09:30 PM


The best way to know which slow jet you need is if the bike runs/starts better once you adjust the idle mixture screw for it. The idle mixture screw must be adjusted for the pilot jet that you are using. They work together. If your bike is idling the best with a 68s at almost three turns out then a 70s should work great. It seems that if your XR650R idle mixture srew can be adjusted all the way in with a 70s and still make the idle raise up, then drop off, then it is the best jet to use hands down. It seems to not be to far out about .75~1 turn to be spot on. I didn't have trouble with mine till 6800 feet about sea level were the adjustment screw didn't help the idle much at all anymore so, I just turned the idle up till I got back down the mountain. A 70s is the outer limit. Some like the 70 pilot. I ride mostly 2400 to 5000 feet above sea level but, do go as high as 8600 feet once a year and sea level (Pismo, on the beach and Mexico). It is much drier here and much different weather so, not the same as where you live and I use a pumper carb. now.

  • drop

Posted May 10, 2007 - 02:43 PM


Thanks man. Which one do you think I should start with?

  • DiabloCaballo

Posted May 10, 2007 - 09:44 PM


Start with the 68s, you probably won't need the 70.

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  • Ramcc4x4

Posted May 11, 2007 - 04:02 PM


I used the 70s when I opened up the side panel. That took the low end flat spot away.

  • Kawabuggy

Posted May 11, 2007 - 06:55 PM


I'm running a 68S in my XR600r, and think I need to go to the 70S. I am at 2.5 turns out on the fuel screw. I tried running it in more, but the bike runs worse and worse the further I turn it in. I think I am going to the 70S. I am at sea level.

  • DiabloCaballo

Posted May 11, 2007 - 09:44 PM


I didn't catch whether you were on a 600, 650l or a 650R, but you should check out this web sight. www.xr650r.us/jetting/ good luck:thumbsup:

  • drop

Posted May 11, 2007 - 10:34 PM


Sorry, I'm on a 650R. I guess I'll try the 68s first. I was leaning towards the 70s due to the full exhaust system I added and the cold temperatures I ride in.

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