Re Jetted 2003 yz450f


6 replies to this topic
  • Mazzeppi11x

Posted July 07, 2009 - 01:51 PM

#1

Well I had a slight bog issue with the stock jetting with my jardine rt-5. so i went 168 main main jet and 45 pilot jet (one step up from stock each). The bogging has gotten worse at 1/4 throttle when i roll the powerr on. What other changes do i need to make? (jet needle, pilot screw, etc).

  • 642MX

Posted July 07, 2009 - 03:54 PM

#2

What made you think it needed more pilot/main jet?...

  • Mazzeppi11x

Posted July 07, 2009 - 04:00 PM

#3

because it bogged slightly with the stock jetting. and the parts guy at my local shop said to go up on both

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  • 642MX

Posted July 07, 2009 - 04:08 PM

#4

because it bogged slightly with the stock jetting. and the parts guy at my local shop said to go up on both




The first thing you need to do is find your correct fuel screw setting. Start the bike, warm it up for a minute. Turn the fuel screw all the way in until the engine wants to idle down and possibly stall, slowly turn the screw out until the RPM peaks and exhaust note is crisp (this is what I call the sweet spot). Now, if the sweet spot is less than 1 turn out, you have too large of a PJ. If its more than 3 turns out, you don't have enough PJ.

Find the correct pilot setting/jet first...

  • Mazzeppi11x

Posted July 07, 2009 - 05:36 PM

#5

your not talking about the ide screw are you? because i did what you said on the pilot screw and from dying to it starting to rev up is about 1.5 turns

  • 642MX

Posted July 07, 2009 - 06:08 PM

#6

your not talking about the ide screw are you? because i did what you said on the pilot screw and from dying to it starting to rev up is about 1.5 turns


Yep, fuel screw... not the idle screw.

You say from stalling to rev up, is that 1.5 turns from the screw being seated? And did the RPM actually peak, or did it just start to rev up?... You can also keep turning the screw out until the idle falls a little and the exhaust note sounds dull (just to be sure you found the peak).

  • grayracer513

Posted July 07, 2009 - 06:12 PM

#7

your not talking about the ide screw are you? because i did what you said on the pilot screw and from dying to it starting to rev up is about 1.5 turns

The pilot screw is the idle fuel mixture screw on the bottom of the carb. Your pilot sounds rich:

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

If it bogged, and you went richer and it got worse, what do you think that says?

Read:
http://www.thumperta...699#post2881699

http://motoman393.th.../tech/carb.html





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