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PeterJ

Idle problems XR650R

7 posts in this topic

Anybody had problems with a high idle condition when coming into tight corners or dual sporting around town? I think it has something to do with the bypass circuit on the side of the carb. It seems to do a good job of reducing engine braking but maybe they get sticky? All it takes is one blip of the throttle and it idles down. I haven't had time to look into it. What ya know guys?

:):D :D(Just for good measure)

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Based on the symptom of 'a high idle condition when coming into tight corners', it sounds like you might be running too lean either due to jetting or more likely an air leak between the carb and intake. When you let off the throttle, the manifold vacuum skyrockets and this is when the intake seal is more prone to sucking in air, thus leaning the mixture resulting in a higher idle. You generally don't notice intake seal problems when accelerating (low manifold vacuum) unless the seal is really bad, but a slight leak tends to show up more so on deceleration (high manifold vacuum).

If you rejetted your carb recently and the problem started after rejetting, then verify you're using a big enough pilot jet and perform a fuel screw adjustment.

It could also be the bypass circuit just as you said, but don't forget to check the easy stuff. Good luck!

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Hi. Qadsan gives good info there on high idles and the cause. But there is something else that causes that especially on the 650R. First of all, is your bike new or fairly low time? When new, it's common on some of the bikes for the throttle to stick slightly open when you let off the gas. As the cables stretch and the carb piston loosens up, it will go away. The reason I suspect this, is because you say when you blip the throttle it goes away. Does it also go away if you force the throttle closed by hand (twist the grip fully closed instead of letting it snap back)?

Of course all of this is just guesswork, since I don't know how much time is on your bike, or if the carb intake boot is truly tight. Qadsan is right, an airleak at the intake boot will cause a high idle and you should check that first of all. But the other cause I listed can also do it. Good luck with it!

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:thinking:Less than 500 miles on this BRP. Good points, especially the throttle slide sticking up. There is plenty of play in the cables I think. I'll check things out and let you know.

P.S. Where did that computer smashin' gremlin go. This is my third attempt to post a reply!

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Is the bike stock? or have you uncorked it. If it's stock it's most likely lean like qadsan said. Well in any case it still sounds like it's running lean. Do you here any poping when you back off the gas?

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Yes - I had the same problem and hated it. The way I fixed it was to pull the cover off the bypass, pull out the diaphram and nip off the little rod in the center of it.

Put it back in and go.

Bang Bang Betty and I am going to be tearing up the Tennessee mountains for the next couple of weeks so I will be signing off for a while. See y'all later. :)

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Thanks for all of the input guys. Everything checks out negative except for Dutch's point. I'll make a new post when I get that check valve bypass thingy apart.

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