2006 YZ250

[Numkut]

Ok just broke-in my new bike, put ina new plug, fresh gas and everything. Then when I went to gas it (1/4 starts getting alittle rough) it starts stumbeling and its not good. I thought it might be runnning rich because alot of smoke is coming out up top. At 1/2 throttle I am losing power instead of gaining power. I leaned out the main jet from 178 to 172, made worse if anything. Then I tried raising the clip on the needle, still the stumbeling presists. It runs just fine from idle to 1/4 picks up good, I don't know whats going on... Moto814 (don't know if you guys know him, runs business focusing on 2strokes) suggested maybe powervalve stuck closed, but I don't even know where or what a powervalve is... Remember this is a brand-new bike, thinking about bringing it to dealership and making one of their mechanics ride it, any ideas?

[Toomey]

I seriously doubt that it'd be the powervalve on such a new bike.
Was the bike running good while you were breaking it in, did you ride it up and down the street at before?  Like what I'm saying, did this happen only after the new plug and gas, or was it probably happening the whole time?  Tough question on such a new bike.  How easy does it start?  And how did the old plug look?

[Numkut]

It never changed drastically, I have experience riding two-strokes and its like nothing I've ever felt. We fiddled with jetting all day today nothing seemed to help. I'm thinking its a factory defect, they'll be hearing from us tomarrow.  Starts, idles fine, idle to quarter throttles ok. When I was breaking it in I never got on it enough to feel it. I just did 3, 5 min. heat cycles allowing it to cool down completely between. Then rode easy for another 10, then changed gas/plug. Then when I went to ride it like I normally would it started acting funny...

[PHN]

Try a different plug...maybe a bad one ...can't deliver spark under load..or the wire isn't on tight...