jetting maybe?

[HK_Shawn]

help!
i have a 92 kx 500 that i just picked up. when purchased the bike wouldnt hit power band and chugged down low. i tested compression and it was at 85psi. i redid the top end and while it was apart i cleaned the carb and checked kips function. now that the bike is back together its still doing the funky rev thing, its almost like its hitting a rev limiter when the main is supposed to open. the crazy thing is when i shut off the gas and let the bike run to eat up the fuel in the carb it cleans up and revs right before it runs out of gas. heres what the carb is set at:
main 168
pilot 60
#3 clip
1.5 turns a/f
40:1 mixture
while it was apart i checked float level

bike has stock pipe and pro circuit can
no lid on the air box and an K&N filter

am i missing something?

[HK_Shawn]

forgot to mention this is at sea level

[Hillclimb#42]

I would be looking at the reeds and main jet. Main jet would be easy to check for debris without much disassembly. I was told that the reeds only affect bottom end before, but from experience, I found that with broken petals the bike started, but would not rev.  More throttle equaled more bog. I'm confused a little that you say that you shut off the gas to run it out of gas and are surprised it revs before it dies. Not sure about that method helping with longevity either.
  You should always know if it starts revving off of idle for no reason, the carb is out of fuel and the air/fuel mixture is leaning out causing a rev. Sometimes you forget to turn the gas on after a break, or just plain run out of gas, even a clogged petcock with a slow flow acts like that. It can Braaaaaaaaap, and take off like a rocket with just a little throttle when its almost out of gas. Scary on a 500.
  No power at the top-end is not related to that. You called it probably, when you said it happens when the main should open. I blow through main jets onto a piece of paper to analyze what got in there and how.  Is it smoking like a mosquito fogger when this happens? If so, could be crank seals. Good Luck.

[HK_Shawn]

the reeds are brand new vforce 2's, i put them in with the new top end.
i ran it out of gas because i was going to pull the carb, thats when i noticed the improvement under lean condition.
the main jet is clean, ive taken the carb apart about 10 times now and check it every time.
ive adjusted the needle from one end to the other and it doesnt effect the way it runs.
i also drained the crank case to see if the crank seal was sucking but that didnt make it run better either.

is there a chance that the ignition is weak and it will only fire when lean?

thanks for your help and keep the ideas coming.

[Hillclimb#42]

 The weak spark issue has come up several times, but I have never had a spark issue, so I am either lucky or they are rare. Other guys had troubles with low rpm spark, but their weak spark condition was helped by revs. Have you checked the pipe and silencer chambers to be sure that they are all clear? If the gas is on and you lean it way over gas comes out, then when you stand it up gas stops pouring out of the overflow, right?

You might try to add more description, too. I get that its not revving out. Is it revving there quickly? Is it loading up at an idle? Its fresh fuel too? No way its contaminated? Just ideas, not trying to be insulting. I remember BDI or somebody having a choke valve that broke or something that essentially kept the choke on.

Good choice on the reeds. They work well.

[mr.5thou sand]

i got 178 main 3rd needle position 42 pilot for av gas and desert gearing
runs so strong all the way trough way past the top end

[DoldGuy]

Be sure your float needle is working, as it sounds as if it is leaking causing a rich condition.
You can also start the bike & let it warm up as you have, turn the fuel off & run until it starts to run out of fuel (when you said it revs clean). Turn fuel on for 1-2 seconds & turn off (you just half way filled the float bowl) & start it up. If it runs clean, you have a float level or float needle problem.
Hope the info helps.
DoldGuy

[HK_Shawn]

while redoing the top end i cleaned the pipe and the silencer is brand new, so no issue there.
the gas is fresh cam2 100 octane, im using maxima castor927 premix. i think i mentioned 40:1
the carb has a brand new choke on it, another thing replaced while doing the top.
the viton tip on the float needle looks good, no wear or chips. i set the float at 16mm 1st time around and have adjusted it 2-3mm in either direction with no results. if i blow through the fuel line and lift up on the float it stops the air flow.
opend up the flywheel/stator cover and the removed the flywheel. everything looks too new for a 17 year old bike so the previous owner may have replaced it.
ill try to get a video of it running this evening to post up so you guys have more to go by. im also trying to track down a buddy with a kx250 to try and borrow his cdi box and coil.

thanks again.
-shawn

[HK_Shawn]

changed out the coil with no improvement. alos tried leaning the bike over till fuel ran out, stood it back up and the fuel stopped. i started turning the air/fuel screw out and it seemed to get "crisper" the further i came out with it.

when a cdi box fails does it just stop working or does it kind of "death rattle" and weaze till its dead?

[kx666]

what about the KPVS governer? is it set correctly/working?

[HK_Shawn]

it has the standard overclosing issue but everything else seems ok. when i rev the bike and the arm moves out.  wheni did the head i cleaned the valves with out taking them apart, i didnt want to risk screwing up the timing. does anyone have a picture of the kips "drums" in the open and closed positions?