08 yz450 carb tuning( i need suggestions)


4 replies to this topic
  • Davos

Posted October 05, 2008 - 06:07 PM

#1

So today i rode gorman, I turned the fuel screw in to 1 3/4 and the bike ran so much better!!!

there is no more bog from 1/2 throttle to full


There is still a slight hesitation right off idle, till 1/2 throttle. the bike likes to flame out while idling.

also when i rev it to about 1/2 throttle, the bike sounds like its burbling, (is that a word) its not a steady running engine, it sound like its gurgling... also i have a slight decelaration pop, which seemed to get better after leaning the bike out a bit.

Can anyone suggest what my next step should be? Im thinking i should try the 48 pilot jet..


My bike is running the twin air airfilter, and the stock headpipe, with a factory 4.1 titanium pipe.

  • grayracer513

Posted October 05, 2008 - 06:36 PM

#2

> When you say that you rev it up to half throttle, are you really talking about half throttle, or halfway up in the rev range? How much load is the bike under when the "gurgling" takes place? What gear?

> Is the "gurgling" a regular miss (dat-dat-dat-dat), or irregular and erratic, even crackling at times?

> At what altitude were you?

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  • Davos

Posted October 06, 2008 - 01:40 PM

#3

When you say that you rev it up to half throttle, are you really talking about half throttle, or halfway up in the rev range?
[COLOR="Blue"]When i say half throttle i mean sitting there in neutral, and opening the throttle to a little less than half throttle. so the bike does not hit the rev limiter. [/COLOR]

How much load is the bike under when the "gurgling" takes place? What gear?

[COLOR="blue"]It never gurgles in gear, only on flat land, it kind of surges while running under half throttle in any gear, it will feel like im letting off the gas a little. [/COLOR]




> Is the "gurgling" a regular miss (dat-dat-dat-dat), or irregular and erratic, even crackling at times?

[COLOR="blue"]Its hard to explain exactly, im thinking i should take a video of it, but it just does not sound smooth at all, its a regular sound, not erratic, it is basically a hesitation that does not go away until i pin it full throttle. [/COLOR]

> At what altitude were you?

[COLOR="blue"]I run anywhere from sea level (pismo beach) and then the highest i go is California City/Dove springs/jawbone/spangler hills which i believe is 2200 feet.[/COLOR]

  • Davos

Posted October 06, 2008 - 01:42 PM

#4

Also worth mentioning, The bike does hesitate slighly in any gear and 1/4 to half throttle, also the bike flames out alot after idling for a couple seconds. when i try and give it gas it just flames out.

I hope this helps.

  • grayracer513

Posted October 06, 2008 - 02:11 PM

#5

To start with, don't put too much stock in what it does in neutral. The timing map is altered then.

I think I would be prone to trying the NFPP needle (5TA-14916-PP),a Todd did in his set up:

http://www.thumperta...050#post5380050

This needle is a half step richer in any given clip groove than the stock NFLR is between 1/4 to half throttle, and one step richer between 1/8 and 1/4 throttle.

If it gets worse, you were too rich already, but it doesn't sound like that's your problem.





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