Idle Screw Help

5 replies to this topic
  • BBD

Posted January 11, 2006 - 10:14 AM


I just got done removing the auto decompressor from my BRP. It is largely stock, save jetting and HRC insert. The problem I have is that I didn't take note of where the idel speed screw should be set. I don't mean the air screw, which I know changes idle characteristics. I'm OK with that at 1.5 turns or so. But I have no idea where to set the other screw and I don't want to flood the thing, then wear out my leg getting it started. I haven't run it in a while and it is bound to be pissy at first.

00 XR650R
03 CRF150F

  • BBD

Posted January 13, 2006 - 11:59 AM


C'mon Thumpsters, help me out here. There has got to be somebody who knows. Or somebody willing to go out to their bike and check.

  • oldturtle

Posted January 13, 2006 - 02:33 PM


The best setting for me is just a seat of the pants setting. Here is how I set my idle on all XRs. First crank up idle so it is plenty high and then start up. Ride until bike is completely warmed up and idle peaks out. Now turn idle down so that idle is smooth but well above stall setting. Shut off and start hot with no throttle. Bike should start and idle smoothly with only an easy push on kick start lever and idle smoothly with no throttle. You know you have it right when next morning for cold start bike will start with full choke and no throttle and go into smooth idle. Many guys will crank up idle for cold start and then when hot will turn idle way down. I don't like this setting because off idle throttle response is too jerky and also hot starting is more difficult. Just avoid temptation to keep turning idle way down.

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  • BBD

Posted January 13, 2006 - 03:01 PM


Thanks OldTurtle. I'll use the method once I get it started. But the problem is, I don't know where to start. Imagine the carb is off the bike and the idle screw is removed. Now put it all back together. What's the initial setting? 2 turns from contact? 5? 1?

  • miguelitro

Posted January 13, 2006 - 04:28 PM


I recently went htrough this, well kinda, when i broke a throttle cable on a trail ride and had to crank up the idle and "cruise control" 10 miles back to the truck.
I got it back into specs by first not turnin it down enough and the bike was backfiring, actually shooting fire! then i had it too low and it wouldnt start, of course i couldnt use the throttle to help set it.
I would start with it low and put some tension on the throttle, start with a little and if it wont start hold it a little more on until it fires up. then adjust you r idle screw to that point, let the bike warm up as turtle said and fine tune.
its really not rocket science adjusting hte idle and as turtle said its a seat of the pants thing with a little personal preference where you want it.

  • BBD

Posted February 27, 2006 - 12:35 PM


Well, I got it started and here's the answer for future reference:

Back out the idle screw all the way until the tip is not touching the the carb cam. Then screw it until it just touches. Then give it two revolutions. That's a good starting point. 2 turns in from full out.

Yes, I know it will be different for each bike. Yes I know that you have to fine tune it after the bike is running. But if you are putting the bike back together and need a starting point, this one worked for me. I ended up adjusting it some after it warmed up, I think I turned it down a bit.

Also, this is the first time I've run it since removing the auto-decompression system. It now starts easier and runs better. It even started easily (like 3 kicks) on a 40 degree morning. Highly recommended mod. I haven't yet had a problem with it kicking back, and I've started is a dozen or so times.


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