Maintenance & Technical > KX500 Original
#8 slide versus #7
Friar-Tuck:
Pegger,
Here's a pretty good readers digest version of carbs/Jetting
http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml
Your bike ought to be able to Idle without loading up, I do not profess to be an expert, however myself and best riding buddie have kx500's, 2000 & '99 respectively.
Minor port clean-up, KIPS bolt mod, aftermarket air filter, reeds and pipe. We ride from 3000 to 4500' (usually)
We both have come to settle on the 52 pilot N8M2 needle (2nd or third clip) 1 1/2 (or so) on the air screw and 168 main and yep, #7 cut-away.
The only thing we have had to change for the winter / summer is clip position on the needle and a little tweak on the air screw.
No more spooge or fouled plugs and the inside (end) of the silencer is Nestle Quick to Coffee Ground Brown (un perked) =) .
I use a 7 heat range (NGK) plug account Mike rides alot Harder than I do. He's got an 8 in his.
The Team Green guys chart use a 9 if I remember correctly 'cause they Haul Mail!
Mike uses Maxima 50:1 and I use Blue Marble 60:1
We figured less than one turn on the airscrew - smaller pilot.
(Turning an air screw in restricts the air flow, and richens the mixture. (turning it out leans the mixture by letting more air in).
More than 2 turns out larger pilot.
You are correct on the slide: #6 would be More rich.
The best way I know how to describe the cut-away is like when you spray a garden hose with your thumb to modulate the spray.
If you squeeze your thumb over the tip, the water shoots out harder and faster.
A carburetor?s slide works just like a thumb over the open end of a hose. You increase the force of the water by decreasing the size of the opening, the same can be done with the Air flowing through the carb.
From off idle through 1/4 throttle opening, the slide cutaway determines how much fuel is picked up by increasing the air speed.
It doesn't do this by allowing more air into the engine. (that is handled by the frontal area of the slide and its relative position in the carb body)
It does it by changing the velocity at which the air streaks under the slide; just like you do with your thumb over the hose.
The velocity of the air draws gas through the pilot and needle. Since there isn't much air velocity at small slide openings, the cutaway is used to create more velocity.
(Kind of a venturi in a venturi) I hope this makes sense...
Tuck\o/
kxpegger:
Just put a #7 slide on order. I'll give a ride report hopefully by next weekend. Plan to put the needle back on the 3rd position to compensate for the leaner slide. Hopefully all that will be left to do is play with the air screw and idle adjustments. The thing screams pretty good already but hopefully it will scream just a little louder when first coming off idle!
KX500freak:
--- Quote from: Friar-Tuck on January 03, 2009, 11:15:59 AM --- Pegger,
Here's a pretty good readers digest version of carbs/Jetting
http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml
story
Tuck\o/
--- End quote ---
thanks friar-tuck
i learned also from this explanation ,esp.about the working of the slide
i had similar issues once ,putted in a smaller pilot jet and a slide 7 which wasn,t there too
now it blast straight from idle too maxrev,and idle without surge ,but i don,t wan,t idle
but it can.
freak
kxpegger:
I finally got the AF back out today. I was on standby call at work for a couple of weeks and had to wait for the slide and needle that I had ordered to show up.
#7 slide and a N82M needle with a 55 pilot and 170 main solved all my tuning issues. I left the needle on the middle position (3rd) and now the bike snaps off idle and screams all the way to redline! I ride mostly Las Vegas around 2500' and it seems to be perfect.
I received the bike from Service Honda with a #6 slide, 55 pilot, 175 main and a much richer needle.
Just wanted to say thanks to everyone that helped and all the accurate info posted here.
serafin:
kxpegger I'm in Vegas also. Here is what I run. Float height 16mm, 165 main jet, 55 pilot jet, #7 slide, n82m needle with clip at #2 from the top, airscrew out to peak rpm aprox 2 turns, NGK BR8EG, fuel mixed at 40 to 1. Was out at APEX for a short while today drop me a pm lets go riding sometime.
Serafin
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