how would your stock YZ4xx respond if you richen up the mixture...


10 replies to this topic
  • Shane_Bettin

Posted September 16, 2004 - 07:54 PM

#1

everywhere quite a bit. say your around 900 ft abover sea level 5 -15 deg. celcius.
ex.
-main jet from a 175 to a 182.
-needle(JD) from the 4th clip down to the 5th clip.
-fuel screw from 1 1/2 to 2 turns out.
also clean air filter.
thanks
shane

  • Hamish

Posted September 16, 2004 - 09:02 PM

#2

due to the low temperature you ride in, it could benefit from a richer mixture.

  • ovrrdrive

Posted September 17, 2004 - 01:17 AM

#3

everywhere quite a bit. say your around 900 ft abover sea level 5 -15 deg. celcius.
ex.
-main jet from a 175 to a 182.
-needle(JD) from the 4th clip down to the 5th clip.
-fuel screw from 1 1/2 to 2 turns out.
also clean air filter.
thanks
shane


Are you asking if these changes would help you, or are you saying you made these changes and it helped your bike and you're offering this as advice to others?

  • Fastest1

Posted September 17, 2004 - 11:52 AM

#4

I am with Ovrdrv. Did you do all of those changes at once? I so, you did too amny at once, go back to the way it worked best last and then go from there. If you are changing elevation (going higher) you should need smaller jets and settings. The signs of too rich, hard to start when warm, sputtering under load, dying if too rich. The same as pulling the choke while running. There is no power being too rich.

  • Shane_Bettin

Posted September 17, 2004 - 04:16 PM

#5

ok maybe i worded it wierd or somethin but im just asking what YOUR bike would do if those changes where made. whatever jetting you have that makes your bike run good now, how would it run if you made those changes in the abovr post. i want to know this because my bike was running great and then since did a couple changes it seems to be runnning very lean according to the plug no matter how big i go with the jets.

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  • YZ250F_Rider

Posted September 17, 2004 - 04:24 PM

#6

well the next question is, just how are you checking the plug?

You chopping the throttle at wide open and insuring the engine doesnt spin so the plug doesnt get contaminated? Or just kinda looking at the plug after riding for a while?

  • Shane_Bettin

Posted September 17, 2004 - 05:58 PM

#7

ya im actually just doin it after a few rides. [@#$%&*!] i guess i haven't been those plug tests right. well after each ride i have to go down the streets to get home so im usually goin real slow, like idle in third for a bout a minute. wouldn't that make a difference? last plug i pulled out the centre was as white as it was new. the last ride was on streets, onlying opening the trottle to about 1/2 the whole ride. i was told today the timing would make it run lean. i checked it and it looks good. ive the 03 cam so im using some 03 cam mod pictures from here. i dont' know what to try next!

  • YZ250F_Rider

Posted September 17, 2004 - 06:33 PM

#8

well you really have to check the plug at WOT first.

That requires you to kill the motor at WOT after 20 or 30 seconds running time with the kill button and grabbing the clutch at the same time so the motor doesnt spin any more (3rd gear). You dont want to risk pulling fuel in with the throttle closed and contaminating the plug. do it with the same plug as it's not all sooted up, and is a bit used. Brand new plugs are tough to read sometimes.

The goal is a tan porcelain color.


then set the fuel screw to factory setting. you can tweak it upto a 1/2 turn either direction. It's a tradeoff between ease of starting and sluggishness of rev when you first crack the throttle.

Then hold the throttle about 1/4 to 1/3 open running for 30 secs or so, and adjust the needle down until it just starts to miss (raise the clip), then lower the clip one notch.

yer done.

  • moto2000

Posted September 19, 2004 - 06:52 AM

#9

since did a couple changes it seems to be runnning very lean according to the plug no matter how big i go with the jets.

What changes did you do? Exhaust cam? I went from a sooty black plug to a plug like you described, just from changing to a auto cam and race gas....no jetting changes. I assumed the clean plug was because of the race gas, but I've also read a couple times now that guys that installed auto cams had different plug readings afterward. :cry: Any opinions?

  • Joe_Jet

Posted September 19, 2004 - 07:29 AM

#10

Did you add the cam with compression release? If the compression release is not set-up properly and the valve is staying open you're going to be all screwed up!

Joe

  • Fastest1

Posted September 19, 2004 - 06:40 PM

#11

If you thought it was lean with your latest settings, it must have been very lean before, according to your records. What makes you think it is lean? Anything besides a plug chop? The question is, does it run better now than it did with the last setting? Has the weather changed? It would have to been a lot cooler to support those new settings if it was running great before. :cry:





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