just had the top end rebuilt with pro-x pistons d-plate&chip rebuilt carbs re jetted 110 pilot jets one turn out on low speed adjusters,125main jets 1-1/4 out on high speed adjusters 1.5 needle&seats 42-45 avj.pop of pressure, lasted one tank of gas,pre mix 50.1 and injection pump for break in..it ran good first tank then seized..started back up with #1 30psi #2 120#3 120 power valve looks ok looked into cylinder with a borascope could see piston has a small hole in the front port and rear ports..before the work was done had a back fire wounder if it took out the front seal..any advise thanks.