im in the same spot with my 87 lt 250. got it about 2 mons. ago, blew it up 2 days later, got it back together, 2 wks, melted the piston again, did that 2 more Xs, and now its time to bore. i call up trinity and they told me what i was doing wrong, staying in the gas in top gear too long(1st 2-stroke, use to riding 4-pokes)