#8 slide versus #7

[kxpegger]

I bought a KX500AF from Service Honda. The bike was slightly sluggish off idle and seemed to go flat a little early on the top end. Took the carb apart and found a 55 pilot, 175 main, CEJ needle and a #8 slide.

I left the pilot alone at 55 but replaced the main with a 170. I can't find a CEJ needle in any charts so I'm going to replace it with a N82M needle. My question is that the combination of jets and needles is recommended by Team Green for my altitude and temps but with a #7 slide. Will this work with a #8 slide instead of a #7. I don't have a #7 on hand. Is there a way to compensate until I can get a #7 slide?

Any help would be greatly appreciated!

[KXcam22]

KXpegger,
  A #8???  I don't recall anyone running a #8 with any success. Hovever, it only really adds extra air at idle to 1/8 throttle so you might be able to tune it out.  I am surprised that it had a 55 and the #8. Hmm.  AJ should be able to tell you if this is a known good setup from them or maybe a mixup on the slide.  It is also possible that since the AF runs a different pipe (similar to CR500) than a normal KX500 that this jetting may be different.  Hope this helps. Cam.

[kxpegger]

Every thing I've been able to find says a #8 is for 250cc not a 500cc. As you mentioned this may be something that Service Honda came up with because of the FMF pipe they use for the conversion. Maybe AJ will chime in?

[Friar-Tuck]

 The CEJ is a  Keihin Needle ID.    The N82M is a OEM ID.
(Here's the conversion & needle legend)               http://www.sudco.com/vol33/135-136.pdf   

  I wouldn't be surprised if the bikes are jetted "Safe" for sea level and 70 deg. 
You might be able to find AJ's e-mail on the site and just drop him a note. He is a stand up guy and has responded promptly to other guys questions.
(I'll snoop around for the needle charts)
  Tuck\o/

[kxpegger]

Thank you all for your responses.

I'm going to try and run it today with a 55/170/N82M and the #8 slide. If it runs goofy I'll bring the bike back home put a #7 slide on order and grab one of my other bikes to ride.

The problems I've been having are from idle to about 1/8th and I think the #8 slide is probably the main culprit. The motor is not crisp off idle and the bike surges quite a bit. I've had to turn the idle setting way up so the bike will start after it gets good and warmed up. Bike starts cold no problem.

[DoldGuy]

KXpegger,
Keep us posted, I am curious if the #8 will actually clean up the bottomend (and a bigger pilot) with out running lean. I have multiple slides, but no #8's to try. Sounds as you have other bikes (PWK Equipped?) check what # slides they have. The smaller the bike the smaller the cutaway I have found (250 #6 slide / 125 #5 slide). Oh and by the way, I am envious of all you aluminum framed guys

[Hillclimb#42]

 I think having my idle screwed in too far, made my 500 surge more. Otherwise, I have no useful input, but post your findings. We all want the AF and wish to trade.

[kawsf]

Hello Kxpegger,

The key to getting the 500 to gun good down low is the slide,found this out about 15 years ago.I rode a lot of tight woods,and never could get it to run good off idle.changing to a leaner slide will give the 500 great responce down low.One size leaner was all i needed,you may need more depending were you live. If you dont have a slide you can cut 1mm off the venturi,that will give you one size difference.I have done this many times,if you are in a hurry.Good luck.

[kxpegger]

After I put my reading glasses on it looks more like a #6 on the slide than the #8 I originally thought it was. The #6 is a richer slide if I understand things correctly. I went to the Keihin website and looked up the PWK 72R series carb which is 39mm and they show it with a #6 slide as standard.

My Clymer manual and everything else I've downloaded says I should have a #7 slide for a 2004 motor.

Well, I can see where this is all headed!!!!

I really don't enjoy carb tuning but if all I have left to do is change the slide out I'll be happy with that.

What I've got so far is 55 Pilot, 170 Main, N82M needle #2 position and a #6 slide.

We'll it's back out to the garage to put the carb back on. I'll keep you guys posted on how she runs today with the changes I have made.

Thanks again for everyones help!

[kxpegger]

After I put my reading glasses on it looks more like a #6 on the slide than the #8 I originally thought it was. The #6 is a richer slide if I understand things correctly. I went to the Keihin website and looked up the PWK 72R series carb which is 39mm and they show it with a #6 slide as standard.

My Clymer manual and everything else I've downloaded says I should have a #7 slide for a 2004 motor.

Well, I can see where this is all headed!!!!

I really don't enjoy carb tuning but if all I have left to do is change the slide out I'll be happy with that.

What I've got so far is 55 Pilot, 170 Main, N82M needle #2 position and a #6 slide.

We'll it's back out to the garage to put the carb back on. I'll keep you guys posted on how she runs today with the changes I have made.

Thanks again for everyones help!

The ride went well!

I could tell the second I started it that things were different. It idled a little slower and had a crisper exhaust note. I decided not to mess with the air screw or idle until it got good and warmed up. I took it over to the dunes and really loaded the bike up by being in a couple of gears to high with varying amounts of throttle. I was trying to see if it would ping or load up when I got back on the throttle (pump gas). It did neither! It just kept chugging along and when I twisted the throttle it just went with no hesitation of sputtering. It did surge a bit more than usual so I headed back to the truck to adjust the air screw and idle.

The air screw ended up at about 7/8 maybe almost a full turn and I was also able to turn the idle down and still get it to run. The bike starts when hot now usually within a couple kicks. It will idle now for about 30-45 seconds before it starts to load up a bit but with a couple of blips goes right back to idling. The surging is almost completely gone on flat surfaces with just an extra ping or two when coming down a steep or long hill.

I've noticed a lot of improvement almost all the way from idle to about 3/4 in the hard pack because the revs are already maxed out before I can get to full throttle. The only time I got to full throttle was really short shifting in the dunes just to see how well it would pick-up under a big load!

The #6 slide seems to be working fine so I might just leave it in there. I'm thinking because it was about 45 to 50 degrees today the bike was fine with it. I may have to go with the #7 when things start to heat up here in Las Vegas. Less air density I think means you need less fuel?

Overall I'm pretty happy with the results! Reason for the long post! Still wondering what the recommended #7 slide might do though?

Once again I want to thank everyone for the help. There's some very knowledgeable people at this site!

[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]

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/

   

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