Maintenance & Technical > KX500 Original

Quick Jetting Question

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dmg:
I have a 92KX500 with a FMF Gnarly and Boysen Dual stage reeds. Ride at 3000ft, and ~60degrees today.

Right after I replaced the reeds, I went for a ride, and the bike ran horrible. I expected it to run differently, because the old reed was damaged. Because I expected a performance change, I didn't attribute the poor performance to the fact that I had the choke left on( I'm embarrassed to admit). The one thing I did notice with the choke on the whole time, was that the bike was loaded all the way up to the top, but then had explosive power at WOT.

Does this point towards putting in a larger main jet? Bike runs well through most of the range, but I always feel like it could do better at the very top of the rpm range.

What does everyone think, try a slightly higher main jet?

Hillclimb#42:
FMF gives good spec on jetting. Usually a little fatter than stock. you really should go from plug reading, also. You can retard the timing to get more rev. Actually leaner main would rev higher, wouldn't it? I try to tune the "explosive power" to the bottom, so I am not thrown off by a surprise launch. Usually that's a needle adjustment for me in the past. My two cents.

Friar-Tuck:
  D,
You have a few choices I think
 A larger main and raise the clip.
  Or larger main and needle combination
  Take the needle you have now and richen the first letter
as an example:

A DGN As a ball park
  If  D= 1? 45?   (Deg of Taper)    Try  a C = 1? 34?
      G                                                    G  (same L-1 length)
      N                                                    N ( Same Diameter @ L-1)
But all this will take a few tries to get it where you like it / or should be.
 The other thing is weather changing in a few mos. 
 Sudco and Carb parts may have a minimum on #parts ordered.
I would be willing to buy some of the extra's if you decide to buy some more needles.
  ( I gave away all the extra needles and jets to the guy who bought My CR) 
  Tuck\o/

KXcam22:
DMG,
  You are noticing a disadvantage of a std carburator.  If you were to look at a graph of hp vs mixture you would see a failrly straight line (slope) with a sharp peak at WOT. Essentially, for max HP at wot the mixture must be quite a bit richer than at "almost" wot.  The proplem is that a typical carburator can't deliver this.  That is why they invented the electronic power valve (look at a new KX250), which is an extra enrichening circuit that is controlled by the CDI and the TPS (throttle position sensor) to open at high rpm and WOT throttle.  Without the power valve, jetting for max HP at WOT is a catch 22.  For guys who demand max HP at WOT you end up running a main jet that makes the bike a bit too rich at under WOT.  For single track guys like me who want crisp throttle response up to WOT, but never run at WOT for any length of time, you end up running a leaner main.  Cam.

Spider:
This has worked well for me.

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