Jetting, nearly there, a little help

10 replies to this topic
  • Brettv

Posted December 21, 2005 - 03:22 AM


ok ive just got my bike back together, (replaced cam chain, clutch etc)
now, ill tell you what i did and what its doing in order, and see if you guys can sus out my problem

starting from cold
choke, 2 kicks, nearly fires
no choke - no go
hot start - starts up

runs perfectly while riding as far as i can tell, so i think my main and needle will suffice for the moment. this is when the problem starts

idling - very high
turn down idle screw - slight drop in idle
turn down idle screw anymore to achieve lower idle - it wants to die and wont idle lower
play with fuel screw - revs increase when i have it at about 3 turns or nearly all the way out
any combination of the above the same thing happens, i have a high idle that i cant get down.

i have no bog,
yz timed
48 pilot
170 main
JD blue 3rd from top
any ideas on what could be causing the high idle and not being able to achieve a slower idle?
thanks for taking the time to read this, any input would be very helpful

cheers - Brett

  • Dan_Lorenze

Posted December 21, 2005 - 06:23 AM


I'm far from a jetting expert but your jetting seems perfect for a WR450 but real fat for the older style FCR. Where did you get your specs from?

  • Krisden

Posted December 21, 2005 - 07:46 AM


Its summer here now i would try pj48 mj 168 JD blue 2rd from top for cooler states VIC NSW SA or 165 JD red 4th from top for the hotter States QLD WA NT

In short it sounds rich to me

  • Matty05

Posted December 21, 2005 - 06:02 PM


Its summer here now i would try pj48 mj 168 JD blue 2rd from top for cooler states VIC NSW SA or 165 JD red 4th from top for the hotter States QLD WA NT

In short it sounds rich to me

Don't know about rich, but high or hanging idle usually lean.
choke cuts off air so no choke leaner mixture.

Try 50 pilot or clean your carby.

I'm on 50 pilot, red#4 and 168 main ('05 WR450F). Live in NT.

  • Brettv

Posted December 21, 2005 - 09:33 PM


hmm, 50 pilot hey, see the thing is, it was running and idling fine before
i have done a few mods since though,
carby has been thouroughly cleaned

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  • Brettv

Posted December 21, 2005 - 10:30 PM


ok heres another update, i just started it up again, and the following symptoms are present

dosnt seem to have an air leak, i sprayed wd 40 around the carb and nothing happened

started 1st kick without choke (hot day about 30 C) which is kinda normal when its this temp for it start without choke

then would only start with hot start, once warmed up

while running, pulling the hot start made the revs increase
pulling the choke would make the revs die quickly and the bike stall
turning the fuel screw all the way out would increase the revs a lot.
turining it in, seemed to have little effect

i did have a good idle at one stage, but after a few quick revs it would either die or idle fast again

sometimes if i quickly pulled the choke on then off it would drop down to a nice idle, but shortly after go high again

???? getting frustrating i know!

  • Brettv

Posted December 21, 2005 - 10:31 PM


shit, i forgot to mention that while trying to start with the hotstart it kicks back a fair bit, and backfires

  • Matty05

Posted December 22, 2005 - 03:27 AM


checked your valves lately??? This can mess you around too.

  • Brettv

Posted December 22, 2005 - 03:45 AM


yeah, just installed new valve springs (kibblewhite) and shimmed them accordingly
yz timed

  • Matty05

Posted December 22, 2005 - 03:50 AM


I would try a leaner pilot then a richer one? It doesn't take that long to change.
I still say you lean.
Hotstart just cold air injection.
Hot day requires leaner jetting!

  • Brettv

Posted December 22, 2005 - 03:58 AM


yeah i may swap back to the 45pj just to see what happens


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