Maintenance & Technical > KX500 Original

1984 KX 500 Jetting recomendations

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Friar-Tuck:
  electech,

  This may sound like old hat stuff however keep notes and only change one thing at a time.
And.. this is just another opinion from the internet...just some stuff to consider..   

The easiest thing to try right off is raise the clip on the needle.  and smaller pilot.
 If your midrange cleans up a bit you are headed in the right direction.

You mentioned you all ran a pressure test on the case so your not drawing trans fluid...
    If you are not running the old girl flat out, drop a heat range. go for a short ride and check the plug.  Only reason I'm saying this is I run a heat range 7.  I don't have alot of WOT territory  out hear and run a hotter plug account to keep it clean.
  I know it's an air cooled bike, most guys run ngk 8's and dune riding or maybe racing run a 9.
     Are you running hard enough to keep enough heat in the plug to burn off the oil
  at 65 deg F
 
Fuel /oil ratio : Lot's of Playriders run 40:1 with no problem, I'm not saying jump into it,
however you might sneak up on it if the bike is mostly stock and not ridden all that hard.
 
 Carb: are the needle and slide in good shape and are the jets relatively new.
           If those are original parts they could be out of spec. 
The easiest thing to try right off is raise the clip on the needle.  and smaller pilot.

 Air Filter oiled too heavily .   
    There could be several things going on at once, Have patience Grass Hoppa!
   Tuck\o/

electech:
 Thanks Tuck, we are getting some hotter plugs and switching to iridium asap, the carb is original but you should see the bike it is like new condition and you can tell it was hardly ridden.   We only did the top and bottom end cause we were in the machine just looking things over.  We picked the bike up from a guy who bought it new in the early 80s and never rode it much then put it in storage until we bought it. The changes we have made have been one at a time, this has been an on-going problem since the spring.  We just went through two CR 500s and are now trying to work the bugs out of this ol girl while its cool.  Our weather goes from 70 to 30 and everything in between this time of year.  The bike wont be ridden too hard, we are planning on taking it to Colorado in the summer and doing some trail riding, otherwise we just fire it up on the weekends and run it some.  Im not that familiar with plug problems, none of my bikes have ever had fouling problems and I like to think i can tune a carb pretty good but this thing is something else.  Anyway thanks for the info. Also we are running 32:1 ratio and the air filter is good.

Hillclimb#42:
double check the floats, that has fixed my 250 with a cold foul issue. Does it still foul them after the bike is warmed up? Mine would foul one mostly on the first start-up of the day, until adjusting them a little tighter.
   :-D '84 Beast. Sounds like a good find. Riding them at all wears out parts, so don't be afraid to check it all out, well maintained is way better than sitting still, for all the seals, gaskets, and bearrings. It getting hard to find parts for older ones too, good luck with her.

electech:
We ended up going leaner on the pilot again and swapped to one step hotter
in an iridium an we have not fouled another plug yet. Thanks for the help and suggestions.

Friar-Tuck:
 Thanks for reporting back!
Someone else may come up against this in the future and have some direction.
   It's not every day someone ask's about an '84 with a mikuni!!
    Best of luck, and drop a photo or two as I don't think I've seen an '84 KX other than an ad in a magazine.   And like I said, You might be helping someone out in the future  :-D
   Tuck\o/

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