bike dies at full revs help kx250 92

hi i have a kx 250 92.when i rev it to half revs its fine but then when i open throttle fully and hold it there it dyes off and hardly any revs just like a coil is breaking down. i have changed the plug. put new fuel and right mixture in. cleaned air filter. throughly cleaned carb and it still does the same any suggestions  

Sounds like a main jet or wrong plug issue.
What does the plug read after the issue?
That will tell the tale.  
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smudge67999:
hi i have a kx 250 92.when i rev it to half revs its fine but then when i open throttle fully and hold it there it dyes off and hardly any revs just like a coil is breaking down. i have changed the plug. put new fuel and right mixture in. cleaned air filter. throughly cleaned carb and it still does the same any suggestions

When it dies off, is it loading up (too rich) or acting like its starving for fuel (too lean)?  Does it run up to full throttle then start to cut out or it never gets there from half?  Is it missing (cutting in/out) when its doing this?

I am also assuming it just started this and was running OK before?  
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Dave H 2006 YZ250
(2008 YZ 125 son)

hi the bike revs great at half revs  starts first time hot and cold but when open throttle full dyes down to an idle rev but release the throttle back to half way fine and revs ok in short burst revs fitted new plug  

When was the last time the topend was rebuilt?  
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Nobody's gonna hurt anybody. We're gonna be like little Fonzies here. And what's Fonzie like? Come on what's Fonzie like?

well 2 strokes dont have a rev limiter, so once the revs reches its peak its going to go flat.  

Hey there! Im not certain, but i am pretty damn sure that those KX's (125 & 250) have a fuel cut-off valve, which is triggered electronically. When the bike reaches a certain point, the fuel flow is cut off, causing the bikes rev to slow down. In other words... "STOP REVING ME SO HARD!!!" is what it's saying. It could be worn or broken, and there for kicking-in to early... just an idea  

well i think its either a carborater issue or as simple as a jet.. i would check them out  
champion of 2008 kx race

Sounds like when you did your carb, maybe a jet stayed plugged. Its pretty ease to miss. Do you have any access to an ultra sonic cleaner? Those things work WONDERS on the small, hard to clean holes. A plugged jet would kinda make sence it doesnt die completely, but lets you return to half idle.

I would pull the carb again. Pressurized air is also a helpful tool.  

heres a couple of things i would check. ill start with the easiest and work down.  

1. clean carb again, go through the jets, spray carb cleaner and compressed air through all holes and jets. put it back on bike and see how it runs.

2. check your reeds, your reeds might be chipped and running to rich thus dieing the top end. had that happen on my cr125.

3. check compression. but since the bike runs, i doubt your compression would be that terrible.  my old rm125 had poor compression b/c the cylinder was out of round, and still revved. just didnt have any power. and was a pain to start.

4. pull the cdi box, test the voltage, resistance, all that electrical stuff.  should be a electrical table in the manual giving you all the different limits for the cdi box.

5. might want to check coil, test the resistance there.

6.  go after the stator, check resistance, voltage all that stuff.

7. oh i forgot one, one of the simpler ones, if you havent already,  if you dont have a clear fuel line with a filter. put one on.  could be as simple as a clogged fuel line.

well theres all my lil tricks that have helped me in the past. and i have been playing with 2 strokes all my life. and im 28.  from the time i was in diapers, my dad had a wrench in my hand helpin him on his bikes. anyways good luck. oh and as far as the KX's having some kind of rev limiter.  for a 92, your throttle is the rev limiter.  mine is a 97 kx 250.  and i still yet to find the rev limiter and i have done many panic revs off of jumps.