87 XR650 Twin Carbs


3 replies to this topic
  • Hensley419

Posted April 28, 2006 - 09:30 PM

#1

Hi, I have a 1987 XR600R that's big bored. Any old time XR600 racers have any tips for carb jetting the twin carbs? Setting the delay between the two?

  • timothypg

Posted April 29, 2006 - 03:46 AM

#2

hi. i've got an 86. int. exh. opened up. i use 45 pilot and 132 mains. i have not messed around with the delay between the two, still on original bore. works good here in wi.

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  • Punkin

Posted May 03, 2006 - 09:49 AM

#3

I've got a 48 slow in the primary and 130 mains. The screws in the needle hold downs are frozen up or else I would try a few different needle tapers.
I'm at about 3500' and ride between 3000' and 6000' 45deg winter to about 90 deg. summer.
628 kit FMF header/silencer exhaust wrapped, side panel cutout, UNI and No-Toil air filters.
I have the carbs opening as close together as possible. If your careful bending the synchronizing arm you can move it back and forth a few times with no ill effect. If you can find something to slip in the gap at the top of the arm and mark it, you can always go back to that "baseline" as a reference. As soon as I finish my CR500 project I'm going to try to find "new" carbs to replace the old ones with. I haven't had much luck finding anything on the keihin PH 25 series carbs on my '85.
Rob

  • Border Patrol

Posted May 03, 2006 - 10:25 AM

#4

Back in the day, the trick thing was to put about a #130 in the primary carb, around a #135 in the secondary and a #48 slow jet.

I used to run 138's in both carbs, #48 slow jet, opened-up airbox and about 20 discs in the Supertrapp. The bike was super rich down low and only ran good WFO. I've since gone with "traditional" wisdom and closed most of the holes in the airbox dropped down to #130's in both carbs, dropped back down to a #45 slow jet and reduced the number of discs in the Trapp to about 8. Much better trail manners this way.

I have never tinkered with synchronization.





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