WR 450 08 Jetting problem - high rmp when is cold

3 replies to this topic
  • CharWR450

Posted July 29, 2009 - 08:06 AM


Hi guys. I have just rejet my bike because it was too rich.

Now it runs better, smoothier, no backfire.
But when is cold and start it has realy high rpm at idle. I adjust the idle speed and ride it for 15-20min and when the bike gets hot and close the throttle it shuts down. Start it again with hot start (difficult to start) and the bike stays with low rmp at idle and shut down again. then I adjust the idle speed again but the rpm are not steady. when i give some throttle increase and drop down again.

My bike is a WR450 2008.

Before i was using the jets from the GYTR-AIS kit
Main jet: 175 (GYTR-AIS)
Main Air Jet: 110 (GYTR-AIS)
Pilot Jet: 50 (GYTR-AIS)
PAJ: 80 (stock)
Leak Jet: ? from GYTR-AIS
Starter Jet: 65 (stock)
Fuel screw: stock
Needle Model/Clip position: GYTR AIS 4th

Grey Wire Mod (Y/N): Y
TPS Connected (Y/N): Y
Airbox Snorkel/Lid (on or off): OFF
AIS Removed (Y/N): Y
Airfilter Brand: Notoil sm
Exhaust Brand: FMF Factory 4.1 complete, powerbomb
Average Altitude: 0-1000ft
Average Temp: 60-90

Now i replace the
Main jet: 170 JD
pilot jet: 48 JD
Jet Needle: JD red - 4th
and put a ZIP TY Fuel Screw 1/2 turn (still try to adjust it). :thumbsup:

Now is summer here, about 90f.

Need to go to a smaller pilot-jet?
Or is something else?

  • wartsnuff

Posted July 29, 2009 - 10:32 AM


something is funny

i put the JD jetting kit in with the jets JD supplied... 168 main. red needle in the stock position.. but i am thinking of moving the clip down/needle up!

and my bike is a little hard to start fully hot... ie 3-5 cranks with the starter.

but runs amazing any RPM... 2008 WR 450 F , stock exhaust with after market end cap...

780 Ft above sea level where i ride.

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  • CharWR450

Posted August 13, 2009 - 04:41 AM


The problem solved by it'self!!! just riding around 1-2 times and the bike runs perfect now. probably was the sudden jump to 170MJ and 48 PJ.

:thumbsup: :worthy:
JD is a perfect kit!

  • Yamaharider531

Posted August 13, 2009 - 05:02 AM


i had this problem with a 2004 cr125..when you would pull the clutch in it would bring the rpms up some? it was like in the middle of winter though so it was a tad lean on the bottom end.....i got rid of that turd awhile ago though haha


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