Jetting Similar Between 05 & 06 YZ450F?


7 replies to this topic
  • ccs86

Posted August 16, 2009 - 07:31 PM

#1

Hi guys, first post...

I've been searching and reading like crazy on here, but need a little clarification. A lot of info is geared towards the 06's, which I thought had slightly revised engines.

My 2005 YZ450 seems a bit lean to me. I have a GYTR pilot screw set to 4 turns out. The ideal cold start for me is to pull the choke, and give the AP 4 squirts, then kick. Fires right up.

Also, the 0%-25% TP range is really abrupt.

I've seen a 45 pilot and 165 main recommended for sea level, hot, humid weather, but according to the ronayers fiche, those are the standard parts.

What should I do?

  • ccs86

Posted August 16, 2009 - 07:36 PM

#2

I looked it up and it says a 42 pilot and 165 main are stock on the '06

  • grayracer513

Posted August 17, 2009 - 06:30 AM

#3

My 2005 YZ450 seems a bit lean to me. I have a GYTR pilot screw set to 4 turns out. The ideal cold start for me is to pull the choke, and give the AP 4 squirts, then kick. Fires right up.

If your pilot screw is that far out, and is actually set correctly, your pilot jet is too small.

http://www.thumperta...ad.php?t=327405

There is info on '05 jetting in the Jetting DB Sticky.

  • ccs86

Posted August 17, 2009 - 07:45 AM

#4

If your pilot screw is that far out, and is actually set correctly, your pilot jet is too small.

http://www.thumperta...ad.php?t=327405

There is info on '05 jetting in the Jetting DB Sticky.





I had set it there while riding through the pits. It was really herky jerky at low speed like that and winding it out seemed to help a bit.

I just rechecked it's position and it actually seems to be the opposite. I can bottom the screw out without the engine dieing, it idles rough though. The idle cleans up and peaks at about 1/2 turn out. That suggests that the pilot jet is too rich right? What about the lean cold starts?

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  • grayracer513

Posted August 17, 2009 - 08:15 AM

#5

That suggests that the pilot jet is too rich right? What about the lean cold starts?

Too large, probably yes.

There is nothing abnormal about the cold start you described, and the pilot, while it will affect cold starting, is not the primary metering circuit involved with cold starting; the starter jet and "choke" circuit is, so the change to the pilot will not affect cold start as much as normal idle and idle-to-main circuit transition.

  • ccs86

Posted August 17, 2009 - 08:21 AM

#6

Too large, probably yes.

There is nothing abnormal about the cold start you described, and the pilot, while it will affect cold starting, is not the primary metering circuit involved with cold starting; the starter jet and "choke" circuit is, so the change to the pilot will not affect cold start as much as normal idle and idle-to-main circuit transition.





Thanks for your help gray :thumbsup:

So, I should maybe step down to a 42 pilot jet?

I still haven't found much info that applies to me ('05, sea level, 85*+, high humidity). Should I stick with the stock 165 main?

  • grayracer513

Posted August 17, 2009 - 08:37 AM

#7

If you currently have a 45, yes, that seems to be what's indicated.

Also read:
http://www.thumperta...699#post2881699

  • ccs86

Posted August 17, 2009 - 03:12 PM

#8

I pulled the carb apart today and everything looked really good inside.

It does have a 45 pilot and 165 main.

I guess for now, I'll just order a 42 pilot and reassemble... unless anyone else has any suggestions while I'm in here. Does my situation sound normal for an 05 in my environment?





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