XR650R now backfires, idles randomly (low/high)

10 replies to this topic
  • Shinyboat

Posted August 25, 2007 - 03:25 PM


I have been riding my 2001 XR650R all summer and have had zero problems with it mechanically. Early in the summer I removed my auto-decompresser because it was acting oddly. I have had over 500 miles without it and no problems.

I just moved across Washington 350 miles and had the bike on the trailer. Before trailering it, it ran perfect. I started riding today and it ran prefect until after about 15 miles. It started backfiring (pop pop pop) bad on engine braking. Later the rpm's would drop on idle and it would want to stall. Sometimes after coming off the throttle completely, the rpm's would stay high (up to 3000) and wouldn't come down. Over time it got harder to start. I messed with the throttle screw, but that did nothing for it. It made it fairly difficult to ride because I'd never know when it was gonna idle low/high.

I got home and cleaned the air filer. I took the carb off and cleaned the everything from the throttle valve down. I removed the jets and blew them. There were a few dots of dirt in it but I think I caused those when I pulled the carb off. I put it back together and same thing. I've heard the float could be sticky. I inspected it and it seemed to go up and down fine...I don't know what sticky really means let alone how to fix it. I pulled the plug (had some black on it...it came off real easy and a golden brown was underneath) and replaced it. I fired it up again and its acting the same.

When the bike is on the stand and parked on an slope, it may spill fuel out the overflow.

I'm baffled!

  • VBS-Thumpstar

Posted August 25, 2007 - 07:48 PM


Sheared keyway on the flywheel?

Sean :cool:

  • husky123

Posted August 26, 2007 - 10:44 AM


Check for intake leaks, vacuum type problem. Spray some WD-40 around the intake air boot (manifold) while the bike is running. If it idles up you have an intake leak somewhere. Just another check...

  • BWB63

Posted August 26, 2007 - 10:47 AM


You have a jetting problem. Something got stirred up when trailering and got sucked up a jet or a jet dropped. Don't just try to blow out the jet but, run a jet cleaner through (small wire). It sounds way lean. Also the vacuum tube (the one that ran vacuum to the smog pump) might have came off or you have some other type of vacuum leak.

Wow, the last guy got it writen 3 minutes before I could finish this.

  • husky123

Posted August 26, 2007 - 11:59 AM


I'm quick like that.:ride:

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  • martinfan30

Posted August 26, 2007 - 01:55 PM


sounds lean.

  • deputyperk

Posted August 26, 2007 - 01:56 PM


sounds to me like a float issue, GL

  • Thorpey

Posted August 26, 2007 - 02:52 PM


When the bike is on the stand and parked on an slope, it may spill fuel out the overflow.

Check the float needle (inlet valve) for sticking/residue and then verify the float level. Pissing a little when leaned is common, but if it keeps flowing, there may is someting keeping the float needle from seating. The high fuel level can result in a "rich" pop or backfire plus running crappy. Just a thought.

  • Shinyboat

Posted August 27, 2007 - 08:24 PM


I guess I'll tear down the carb again tomorrow and find out!

  • Thorpey

Posted August 28, 2007 - 10:07 AM


If you don't have the manual, you can download it here.


Also, might want to follow the fuel screw adjustment procedures in the book.

  • Shinyboat

Posted August 30, 2007 - 08:50 PM


I got it working!

I think it was associated with the pilot screw setting. I took everything apart 2x on the bottom end and it worked after the 2nd time. I also rejetted it...I wanted to see how it runs doing so.

Thanks guys

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