Hanging idle because of a rich PC?


8 replies to this topic
  • Kasjok

Posted March 03, 2008 - 10:08 AM

#1

I have a 2007 YZ450F and every now and then it tends to hang a bit on idle. When I start it cold with the cold start knob out the RPMs are about 2500 and when I blip the throttle they rise to about 3600, which is good for knob being out. But the real problem (so to say) is when it is all ready warmed up and it sometimes (not always) hangs for about 5-8 seconds before dropping to it normal idle(about 2000RPMs).

The temp is now about 32 degrees Fahrenheit ( zero celcius) and elevation is from sea level to no more then 700 ft.

Jetting:
48 pilot with 1 turn out
165 main
all else is stock.

I am not sure if this problem is related to my hanging idle, but this bike tends die in corners more often then my old 2004 did. I can`t say it is due to too low RPMs, it like it doesn`t have the power to run or something. It could be just me, however.

One more question. What up with the valve thingy attached to the hose coming from the fuel tank cap? I think I heard that it tends not to work as it should(vacum).

  • grayracer513

Posted March 03, 2008 - 10:28 AM

#2

The check valve in the tank vent is easy enough to check. From the gas cap end of it, you should be able to suck air through it, but it should be much harder to blow air out.

When the bike is running with the choke on, it gets both extra fuel and extra air, so it will tend to run up a bit. Be sure that your hot start is closing all the way, though.

Other thoughts: If it tends to die when you pull the clutch in at speed, it may be rich at idle, but that's not likely at 32F and at sea level. Besides, rich idling causes stalling on idle down, lean idling causes hanging.

Maybe your idle speed is also a bit high.

  • Kasjok

Posted March 03, 2008 - 10:51 AM

#3

My hot start is all good, just checked it. I remember some guy said in forums that he managed to eliminate idle hanging by going actually smaller on the pilot jet. Go figure ...

  • tranqwhl

Posted March 03, 2008 - 11:05 AM

#4

I am putting a bigger carb on my XR; I found that (for me) a lean pilot caused the hanging idle. I had to go huge fat on the pilot to make it stop hanging! It turns out in the end I was just in too far on my fuel screw. I was able to put my pilot back down to a more reasonable level when I opened up the fuel screw.

SUMMARY: Try turning your fuel screw out to 2.5 or 2.75 turns, and then report back please.

:smirk:

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  • Kasjok

Posted March 03, 2008 - 11:26 AM

#5

Well that`s the first thing I tried. I am not sure if it cured this, because with these settings my bike had a lot worse throttle response. I think I try to use a smaller Pilot jet and will report as soon as I have ridden it.

  • TCCRA RACER

Posted March 03, 2008 - 05:59 PM

#6

We run 48 in ours all 5 of them!! And the 08's too.. we get a hanging Idle too sometimes.. It's happened on all ours and our friends..

  • todds924

Posted March 03, 2008 - 09:17 PM

#7

My hot start is all good, just checked it. I remember some guy said in forums that he managed to eliminate idle hanging by going actually smaller on the pilot jet. Go figure ...


Run your fuel screw out to 2 turns...this should cure it.

  • tranqwhl

Posted March 04, 2008 - 07:14 AM

#8

Run your fuel screw out to 2 turns...this should cure it.

+1

that's what I said!

  • todds924

Posted March 04, 2008 - 05:58 PM

#9

+1

that's what I said!


+2....sorry...didnt read what ya wrote!!!!!! You don't want to go out more than 2.5 turns though...if thats the case your going to need a bigger pilot





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