Freshly rebuilt kx250 smokes like crazy and doesnt sound right... help?

I just rebuilt my 2003 kx250 from the ground up almost every nut and bolt and all of the engine (top end, bottom end, complete clutch). it has new radiators and exhaust as well. When i bought the exhaust originally it was racing season and i didn't have the time to re-jet the bike immediately and like an idiot i decided to race it while it was running lean and ended up blowing the motor. so i put in the recommended 165 main jet and 52 pilot jet when i re-built the bike. I finally started the bike yesterday and it started with a few kicks and seemed to run ok. But it smokes like crazy. its insane how much smoke it makes, and I don't want to rev it too much to try to clean it out because its a brand new motor. it doesn't have that characteristic castor 927 premix smell either. I've put like 15 minutes of run time on the motor and it just doesn't seem right. It makes a sound similar to the sound you hear when you slowly push down the kickstart once in a while too if you rev it and that kinda scares kx.jpg

Pressure test to see if you folded a lip on the right side crank seal.

is there any easy way to pressure test it without ripping it apart? and if i did fold it would i need to replace it?

Look in the pinned threads here or in the Honda two stroke forum for pressure testing. If you did catch the seal, you may be able to fix it with a small pick.....carefully. You need to remove he right side cover and primary gears.

How long did you run it? Could be just assembly lube smoke.

Edited by Jeekinz

Here's Pro Circuit jetting recommendations


KX250 165 52 NAFH 2ND 2 50 8.0       Pro Circuit 162 50 NAFG 2ND 1 1/2 50 8.0


These are for sea level at 70*F and 32:1 oil ratio. Given it's likely not 70*F in New York now your MJ and PJ could be right. Verify needle clip position, air screw, and float level though. 

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