XR650R bogs down at speed

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Kortbroek

Race Dog
Joined
Jun 15, 2015
Messages
4,339
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1,246
Location
Port Elizabeth
Bike
Honda XR650R
So I had an interesting new issue on the XR650R the past weekend. At speed (120kmh+) and around 6000rpm  the bike sometimes bogs down and starts losing revs. This only happens when I am accelerating with the throttle wide open, if I back off the throttle a bit it recovers right away. If I roll it on more gently it pulls fine to 160kmh+ and will keep going .  Now I was able to get this to happen multiple times and the common denominator was being on a rough surface. I tried the same on tar and it didn't happen.

My suspicion:
  1) Choke plate might be closing at high revs over a rough surface. Likely the spring holding it open is tired so high revs combined with the bike running over a rough surface could see this getting sucked closed? Might explain the quick
      recovery as soon as I roll off the throttle a bit?  :dontknow:
  2) Another possible culprit could be a blocked breather causing crap at higher revs (not sure if this would actually cause this symptom)?

Then another issue I have picked up over the last few months is a hanging idle. I would set the idle at 1400rpm when the bike is warm, after riding a few km it would idle at 2200-2300rpm and only settle down after a few blips on the throttle.
Now I'm thinking there are a few possible culprits here:
1) Pilot jet mixture screw setting has gone awry.
2) Carb needs a good clean maybe. It is overdue for one anyhow.
3) Leaking carb boots? Also not unlikely. What is the easiest way to diagnose this?

What say the XR brains trust?
 

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