Cylinder works Cylinder kit

Has anyone beside myself had a Cylinder kit from cylinder works start puffing smoke after second heat cycle.
I rebuilt my 19 350 sxf with brand new parts. as stated above. I was thorough, so I thought. Making sure oil rings are at the 1/3 spacing apart end gap was to spec and center ring didn't overlap. The compression ring with the letter up, used a ring compressor to install the piston.
Replaced the valve seals to be sure no issue would come up. installed new timing chain and put the thing back together. New air filter, oil and radiator ice.

First heat cycle was on the stand. letting it warm up to 120 with a ac thermometer in the radiator. Second heat cycle was at a local trail going somewhat easy. Third time I started it after letting it cool to the touch. I noticed a little puff when blipping the throttle just before I went out.

I came back loaded it up, put it away. The following morning started it just to see if it was coincidence. Not a chance. No smoke at start up then the smoke. I pulled the head. checked the valves leak tested barely a trickle.
I thought surely the cir clip must have broke. Pulled the cylinder. nothing evrerythig checked good. I'm at a loss as I have done many bikes but this one is a head scratcher.
 
I'm not familiar with that specific bike, but does it have valve seals and, if so, did you replace them while you had it apart? I know on my Honda XRs, the seals may look good but generally get hard with age and allow a little oil seepage causing mild smoke.
 
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