not running right

[93rm125]

my 93 rm125 has no low end power but when the power band hits the bike comes alive. but when i ride for about 10min when it hits the power band it doesnt do much just seems like its hitting a rev limiter or something. when i shift gears its doing the samething as soon as i shift into the gear. It does that up until i shift all the way thru to 6th then it bogs down and does it. at idle if i give it some throttle the engine stalls then picks back up. when riding the bike i have to give it 3 or 4 good snaps of the throttle to get it reved enough for the bike to stand up. it always has the low end power problems but only starts the stalling crap when the engine seems to warm up. Im sure i got 2 problems. Possible power valve stuck open? But what would make it crap out after awhile? Does anyone know of what the problems can be?

[98sickshee]

check the jets and reeds make sure there clean and that your running right sizes sounds like it could be running lean or rich...2 strokes are hard to tune just take a peak in that reed cage sounds like that could be it