I bought a rebuilt smallframe locally, drove it maybe 100 miles commuting to work.  So, one day when driving along, the scoot seizes...on the flat, at moderate speed & rpms.  Until this happened, the scoot ran fine, and I've had no problems with it.  I think I was premixing correctly, following the instructions of the previous owner.  The scoot did have a 133cc kit on it (don't remember the name). Took it apart & this is what I found:

the jug with the head off  

underside of the head 

the ring, in pieces

grooves in the cylinder wall

Any thoughts on why this might have seized?  Any similar experiences or possible diagnoses appreciated, meanwhile I'm going to try to track down the info on which kit was installed.