Topic: General question: raising the needle vs. re-jetting?

[grumpy]

When tweaking the mixture, when do you alter the needle height & when do you need to re-jet?

I'm guessing it depends on how the mixture is at different throttle settings...

[KingCustomCycles.com]

Here is my take on it..... When I open up the air coming in and going out with pods and pipes, they go lean on me.  Poor excell, popping, needs tons of choke to start, and slow to warm up.  I usually go up a few sizes on the main jet (110-120) and leave the pilot jet alone.  Test ride.  If it is still lean, I will raise the needle a notch. test ride.  If I run out of needle slots and it is still too lean, I go up a few more jet sizes and move the needle back/  Basically, I ball park the jets and use the needle to richen or lean.  I could also do the opposite but then I would need a million jet sets.  Also keep in mind that the needle is a transitional thing, it works between idle and full throttle.  If your midrange is rich or lean, but it idles well and has good full throttle pull,  it is needle adjustment time.   

[grumpy]

Cool - thanks
That's what I figured but I wasn't sure & I didn't want to F it up by going in w/out a clue.

If your midrange is rich or lean, but it idles well and has good full throttle pull,  it is needle adjustment time.   

That's totally what's going on. Idles fine, leans out in the middle (at about 4-5K) then pulls HARD on top.
Needles it is.
THANKS!!

[Tower]

You could also do a throttle snap test at full throttle and a test at 3/4 throttle. 

In general when you snap the throttle open, if the bike hesitates then accelerates, it means the mixture is too rich, if it speeds up then bogs then its too lean.  What you are looking for is smooth acceleration across the entire range.  Test as follows:

Top end (main jets) - Full throttle snap at 7000 - 9000 rpm
Select the main jet that produces the highest top speed. Starting with what you have...if the bike pulls harder at high rpm when cold and less hard when fully warmed up, the main jet is too large. If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small. Run the bike hard for about 15 minutes with any new jet, let it cool off, then move to tuning for midrange power.

Middle range (Needle height) - Full throttle midrange snap at 5000 - 7000 rpm
Set needle height for best power between 5000 and 7000 rpm. If the engine pulls better when cool, but soft when at full operating temperature, it is too rich in the midrange and the needle should be lowered.

[rachet]

Does this forum have a "favorites" folder i can put this in!?!  Amazing and helpful information!  thank you Tower and KCC.com for this very useful information!  And thank you Grumpy for asking what I've been wondering but not sure how to ask.

Rachet~