Jetting!!! Again and again and again!

[gowen]

Zert, sorry. I thought that might be the case but had to give the idea out eitherway. I also keep mine shut. I figured if I perfected the jetting it with them close, there is no need to open.

[zert]

update

Today i put the clip on the needle on the top position, air screw 2.5 turns open and i went for a ride.The respons was very good but still doesn't idle.When i came home,i checked my plug and it was grey/white(too lean but i think that because my main is to smal).So,i ordered a stock needle but i have to wait because here in belgium you have to wait for everyting.I let you guys know how it went.
regards,wim

[alan]

So what happens when you bump up the idle stop?

[Johnniespeed]

Hello everyone. This topic on jetting seems to get beat to death, but it is vital to great performance. So after a couple of years of seat of the pants "dyno testing" I thought I would share what currently works best for me.
  Klotx R-50 mixed 40-1 with premium fuel, BR7ES plug, stock reeds with moose reed spacer.
 FMF Gnarly pipe, stock bore and ports. I live at 760 feet above sea level.
  I have the air screw at 1.5 turns out, my pilot jet is a #45 that I drilled to #46.5  (48 too rich)  stock n82n needle on second clip and 168 main jet.
  The bike starts cold on second or third kick every time. When warm or hot it starts on first kick almost always. It idles smooth and  accelerates cleanly at low speeds. The throttle can be snapped open at any time and it will try to tear your arms off.
 This is, and has been, a work in progess, I have put, as of this week, two hundred and forty gallons of fuel through this bike since it was new two years ago. I feel as though, I have it right, and am very happy with the performance. Now if my riding would improve that would be better.
  KX 500 is the best.  Johnniespeed

[gowen]

That's excellent to hear.. It is a topic that has been beaten to death.. But, I'd say about 90% of the KX500's out there are running at about 60-70% due to the jetting. Most people I've talked to around here that had one at some point in life have all said that they foul plugs and are hard to start and just smoke too much... Which is all due to jetting..

[KXcam22]

I wanted to reinforce an old point: An important starting point for jetting is having your float level set correctly.  Having said that and jetted many bikes I still had forgotten how much difference a small adjustment can make.  My bike runs great but I was losing too much fuel out the carb overflows over rough ground.  Float was set (as always) at exactly parallel.  Strap a beer can on the overflows and you might be supprised at how much fuel is in there at the end of a rough ride.  I once lost 1/4 tank with the bike leaned against a tree while I was eating my lunch (and not paying attention).

My Issue:  Try to stretch out my mileage by preventing as much overflow as possible.  For a trial I deliberately lowered the float level 3mm (from exact level) which is about 1mm below the min spec.  Todays ride gave me almost no lost fuel and a crisper bottom end response. I was pleased at the crisper bottom end since I had noticed a gradual richening over time.  I had suspected needle jet wear (ovaling) but couldn't detect any.  Cam.

[joebloggs]

Just finished a major nuts&bolts rebuild of the 500 hundred from the ground up.its an 89 model and every seal,bearing,gasket and just about every part that needs replacing due to ware and tare has been,only performance mods ive made are a gnarly pipe and hitech dual stage reeds,the trouble is know when i come to start it back up. Checked all all the jets and striped and cleaned the carb but found a 190!! main 62 pilot and a 1 step richer needle!!, what i cant get my head around is that the plug was a nice light tan colour and it started 1st/2nd kick and hardly smoked,it was on 60-1 putoline mx7.After reading the jetting charts i settled on a 170 /60 combination but left the original needle in,but now its a pig to start,wont tick over,smokes like hell even on the same ratio and oil and when it warms up it dies as if its either still got the choke stuck on,wich it hasnt or its running out of fuel,only thing i havent checked is the float height but how do you do it,do you need a tube and an adapter for the float bowl or is there another way? thanks for any help and advice,the forums been a big help over the last 2 years its taken to finish this bike,now all i wanna do is ride the thing!!

[KXcam22]

Joe,
  Welcome to the site!  Next post mention your elevation, average temp and humidity,  bike history and sparkplug type.  Your original jetting was extremely rich. It is possible that the bike was resetted at one time to compensate for air leaking in the crank seals (I'm assuming that you replaced those).  I am aslo assuming that the 89 carb is the same as my 92 PKW39. I think in the 87-88 years the carb float was different. The float can be set "eyeball" to level or you can blow into the fuel inlet and see what level the air stops (see previous posts for exact method).  Level is the setting but I find it is better to run the level 1-2 mm lower (measured at center point of float).  Since the bike is older I would check/replace the float valve. Any leakage will make it hard to jet. The richer needle and 60 pilot may give you some grief. The stock needle is on the verge of being too rich hence I run mine in the lowest position (clip highest).  Have no fear. We will be able to get this thing running perfectly.  Hope this helps. Cam.

[joebloggs]

Bit more info but i think im getting close.Running at sea level at 5 to 15 c,b8evx (platinum plug),new seals in everything,carb is a PKW39,seems unchanged to later models and i think even though its an 89 frame its a 90 plus engine and even newer suspension(2000 on i think).Made a few changes to 55 pilot 170 main and found the float height was at 30+mm,no were near to 15mm to 17mm it shows in the clymer manual,no wonder it felt like it was running out of fuel,reset that and started in 2 kicks,wont tick over for long without reving it but its d**n close,close enough to bed every thing in for know,then ill stick it on the local dyno and get a fuel/air ratio print out and find out what it needs from that, Thanks for help KXcam22 and every one else on here.

[FuriouSly]

Hey Joe...  made my heart skip a beat when I seen the pics of your bike.  Very nice looking.

Glad to hear the jetting is closer for you.  You say that it is revving.  Might want to check the reed boot for leaks/cracks and also the stator side crank bearing seal.  Sometimes masks lean (you say 170 main and 60 pilot).

Sly

[joebloggs]

Thanks Sly,all the seals are new,i ment it wouldn't tick over,i had to keep reving it to keep it runing,but thanks for the advice,glad you like the pics ive hundreds more detailing the whole strip/rebuild if any ones interested ill stick them in the gallery,even have the details on making your own lighing coil and charging system if thats of any use to any one.

[FuriouSly]

Copy...

Definately throw some pics in your gallery that you think we might like   

As far as Tech Tips/Advice...  anything in writing/pictures is always beneficial to the tinkering KX owner   

You ride that Motard on the street??

Sly

[joebloggs]

Too pritty for the dirt Sly,and besides it annoys the hellout of sportsbike riders thinking they know how to corner when this thing comes up the inside of them sideways,then leaves them behind on the back wheel,the look on there faces when you have to stop at some point or they finally catch up is priceless!!!

[hughes]

Dude that is one nasty looking bike, sick as f**k.    the ole 500's can never be to pretty for the dirt.

[raredesign]

Wow, just when I thought it was me, I see this site, and realized I am not the only one with surging problems.

I just purchased an 02 KX500, that had only 25 hrs on it previously. I was experiencing surging on the deceleration, and so I put in larger jets 175 main / 62 pilot. It is better than before, but is still there. It is most prominent when I chop the throttle, and inversely less prominent when I ease off the throttle.

I have received many suggestions about air leaks, or such, but the bike hasn't been used much, and looks fine, nevertheless, at this point, I am not certain.

I am in Rochester NY, and the temperature has been mid 30's.

Thanks all