Top of powerband.

[Uzi9mm]

2002 KX500.  Starts easy and accelerates well.  Pulls wheelies easy through 3rd gear.  But, in the top of the powerband, the 500 seems a little flat and sometimes breaks up a little.  Boyesen Rad Valve, Gnarly pipe, stock silencer, 3 turns out on the airscrew, 55 pilot, 2nd clip down on the needle, 168 main, clean air filter.  100LL @ 32:1, 500ft elevation @ 70deg F.  Could the reeds be damaged?  Could it be timing?  Will the top end be a little flat with a Gnarly pipe compared to a Pro Circuit or a Fatty?    

[KXcam22]

Uzi,
  With the Gnarly the top end loses it's excitement and gets pretty flat.  It's a bottom end and midrange pipe.  168 & 55 sounds a bit lean for 500ft - I can't reacall exactly so you might want to check the jetting chart.  I run 168/58 at 2000'-7000' with the gnarly.  The gnarly shouldn't break up at top end, it just loses its steam.  Hope this helps. Cam.

[Uzi9mm]

Cam,

How did you set your float level?  I cleaned the carb after I bought this bike and looked at the floats.  I held the carb upside down and the floats were parallel with the bowl when the valve was closed.  So, I figured that was good.  I've read that some guys use clear plastic tube that hooks up to the bottom of the carb so they can see the fuel level.  My bike seems a little rich.  When I got the bike the air filter was dripping with oil, there was oil in the boot and the carb.  and the carb had a 48 pilot jet the idle turned in all the way.  The needle was on the top clip.  The bike barely idled.  I cleaned out the oil and put in a new "lightly" oiled uni air filter.  Also, put in a 55 pilot and went to the 3rd clip down on the needle, 2.5 turns on the airscrew.  Until the bike gets hot, it hesitated a little around 1/2 to WOT.  I changed the airscrew to 3.5 turns and moved the clip to 2nd postion down.  Now, the bike pulls hard with no hesitation and idles a lot better.  Still trying to figure out the carburetor.  When revvin high the bike will sometimes break up a little but it revs clean through the mid-range.  You ever run a Pro-Circuit or Fatty?  Do you notice a huge loss of low end when switching from a Gnarly to a Pro-Circuit?   

[Hillclimb#42]

You will probably always have low end juice with the K5. Check out the thread on the powervalve adjustment where they are putting a longer stop-bolt to set the powervalve right. Also, I turned the timing back a tick and got alot more r's out of mine. PC adds hit to top. It sounds like you are running lean. 3.5 turns usually indicates time to re-jet or change needle. Usually you need to get richer with wear and tear. Is it pinging or knocking a little on top end? If reeds are busted its obvious when you look at them. Cracked or broken petals or warped away from cage will cause hard to analyze conditions.
  I kinda noticed that my bike didn't pull 2nd as far as my 250 awhile ago. That basically came down to gearing. What sprockets are you running on that beast?

[KXcam22]

Uzi,
  For a slick method for setting the float level look in the jectting sticky.  It is in there somewhere. Cam.

[Uzi9mm]

Thanks for the replies,

Cam, I will check out the float level deal.  Hillclimb, I haven't changed the gearing at all still running 14/47.  I ride some easy trails and some basic tracks.  I have a lot to learn about dirtbikes.  Haven't inspected the reeds yet.  I will look into the timing too.  No pinging or knocking.  Haven't had the top end off either. 

[KXcam22]

Definitely sounds like something is not quite right.  As a suggestion I would:

1. verify compression with a tester.  No good trying to jet a worn out engine.

2. Inspect your reeds.  You will need a new gasket.

3. Verify the plug.  BR8ES,  BPR8ES, BR8EIX  etc.

4. Set the float height.

5.  Make sure the airfilter is in good shape and not over oiled.

Let us know how you make out. Cam.

[apple]

I`m with Cam on the Gnarly pipe. I had the same problem, switched to a desert pipe and the top end gain was HUGE. I went 1 notch richer on the main jet, 1 richer on the needle clip. I do not need more power now.

[Uzi9mm]

Verified compression @ 160psi.  New Uni air cleaner lightly oiled.  Did not check reeds yet and didn't change float height.  Replaced the old BR8ES with a BR8EIX.  Takes a couple more kiks to start now but cleared up the problem.  The old plug was gapped at 2x what is recommended in the manual.  Thanks to all for the ideas .  Where do you guys order most of your parts?  Like gaskets etc..  I didn't realize that FMF made 2 Gnarly pipes.  Mine is a Gnarly Desert pipe.  What silencer do u recommend, mine is stock and probly needs to be repacked.  Never repacked a silencer, which kit should i get?  Still going through the bike and riding it as much as I can.  I will check the reeds and re-check the floats soon.  I want to ride a couple more times first.