Author Topic: 86 kx500 jetting 39 pwk with shaved head/cylinder thx  (Read 2892 times)

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Offline ironmike

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86 kx500 jetting 39 pwk with shaved head/cylinder thx
« on: August 25, 2010, 12:47:37 PM »
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Hi guys. New to your site. Not sure if im posting this in the right place? I just picked up a 86 kx500. Have a few problems but got it running. Ended up getting a keihin 39 pwk carb from an o5 ktm 125 off ebay. Ive looked on this site to get a starting point for jets? Seen that most of yous are using 55 pilot,168 main? Put those in and seems to be running alittle lean (clip is in 3rd slot down from the top. Put 58 p and 170 main (moved clip back to 2nd slot). Seems to be dumping to much fuel? Its a little boggy. Pulled the plug and its grayish and very wet. Air screw is set 2 turns out. Guy I got the bikr from said he had the head and cylinder shaved .065 and 70 over piston is in there? Mods are pro circuit pipe,answer silencer,duel stage reeds,uni air filter/holes in air box. Let me know your in put and what you think about the set up and the whole shaving thing? Ive always rode 3 and 4 wheelers and havent had to many dirtbikes. Thanks in advance.mike

Offline greencannon

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Re: 86 kx500 jetting 39 pwk with shaved head/cylinder thx
« Reply #1 on: August 25, 2010, 04:20:45 PM »
You need to dial in one jet at a time.  You didn't state what part of throttle position where the bike runs lean. 1/4, 1/2, 3/4 or thru the whole range. That'll help get you on the right track.
I'm sure it's not just as easy as swapping out stock Mikuni for the PWK.
As for the shaved head and jug, it's possible your supposed to be running race fuel with higher compression -  hence jetting woes
never seen a 70 over piston for kx500,maybe old LA Sleeve stuff ??
Sounds like the beginnings of a "Frankenbike"
I have an 87 in theback ofthe garage i haven't started tinkering with yet. oh boy...

Motorrad

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Re: 86 kx500 jetting 39 pwk with shaved head/cylinder thx
« Reply #2 on: August 25, 2010, 04:32:18 PM »
What slide # are you using
what needle # are you using

Offline Friar-Tuck

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Re: 86 kx500 jetting 39 pwk with shaved head/cylinder thx
« Reply #3 on: August 26, 2010, 03:36:15 AM »
Welcome Iron Mike,
 There are a few more Items to consider, Elevation & Ambient Air Temps and what heat range plug are you running, type of fuel,mix ratio, and what type of riding will you be primarily doing.
   
I have to thank you for doing some research and having found a 168 & 55 a good place to start,
( C rider, stock or slightly modded bike at or near sea level, trail or mx, 40:1 from 75 -80 deg I'd say .)
Not that the process isn't the same. The only difference tuning a chainsaw, R/C car and Bike are the way the circuits are controlled.
      Most guys who are new to a bike or site just want to know what everyone else is using, and it appears you know there's more to it than just throwing out some numbers. (Well and be somewhat responsible about it any way.)
  The Teem Green Jetting Chart has been a good place to start, like you stated, you need to do some tweaking.
       Green Canon also makes another good point, where is the lean condition occurring.
The pilot will affect Starting, Idle the most.
The needle and clip position  will have the most effect off idle up to 3/4
Over 3/4 your on the main, remember the circuits all overlap, or The ankle bone connected to the shin bone.
     I would leave the 170 main in it right off unless you are excessively blubbering & spooge-ing.
I don't recall you stating whether or not you were experiencing any detonation or not,
   or you may not recognize the symptoms.  But an ashy white plug might not last long and you may be looking for a stock head, cyl, rod and crank if not corrected quickly.
   Just because the plug was wet, doesn't mean it's not gonna melt down at speed....looking forward to the next exchange of info!  :-)
    Tuck\o/ 
"The Truth Has No Agenda"

Offline ironmike

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Re: 86 kx500 jetting 39 pwk with shaved head/cylinder thx
« Reply #4 on: August 26, 2010, 03:11:19 PM »
hi tuck. Thanx alot for the info. Yeah I do know some stuff but am always looking to learn more? I put the 55 p and 168 m jets back in today. It ran much better. It breaks up a little off idle then kicks in pretty strong in the mid. Seems to die down a little at wot. Maybe I will put the 170 main back in? Good idea? I checked the plug and it was a tannish brown which I know is pretty good. I gave it a hour break(dinner time) then ran it again. I ride about 1/2 mile through the woods to get to a wide open feild. I get the r's up when Im going through the woods so i dont foul the plug. It again was running pretty good. Im pretty sure it can run better. Im just happy its running. I have been working on it for the last 2 weeks in my free time. I couldnt get it started for the longest time until I was pulled behind my buddies 350x. It fired right up from be towed. Before that I kicked it over pro 3 -4 hundred times.LOL! Now it starts pro in 4-6 kicks(tdc). I checked plug again after 2nd ride and it is now grayish in color and oily around the thresds? Oh yeah Im running 110 octain 32 to 1(yamalube ). I also forgot to ask if there is any other piston that I can use for this bike? I know they are discontinued. Which is dumb! I want to keep the bike but want to make sure I can rebuild it if I have to down the road. Is it common thing to have the cylinder shaved also? I know the head shaving is common. Let me know your thoughts? Thax.

Offline Friar-Tuck

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Re: 86 kx500 jetting 39 pwk with shaved head/cylinder thx
« Reply #5 on: August 26, 2010, 06:49:07 PM »
  Yes the needle & slide are probably from the KTM 125.  They can be replaced, the PJ/PWK needles and jets are interchangeable.  PWK slide only fits PWK  There is a number on the bottom of the slide that will tell you what "cut out"
  it is.   Most guys run a #7

Quote
breaks up a little off idle then kicks in pretty strong in the mid..
  Looking either at the needle and /or the powervalve working properly?
The needle has a # stamped around the top 1/4  of it's body
 
Quote
Seems to die down a little at wot
Main and possibly PV not opening all the way.

  Tuck\o/
"The Truth Has No Agenda"