ok,,,i melted a piston 2 weeks ago and bought some stock non ported cylinders with a new bore job and a new pair of vitos super stock pistons. im just curious how many jet sizes i should go up on the mains. the previous cylinders were also non ported as well. i have a weird combination as far as the carbs go. im running a really rich needle with 60 pilots and 128 mains,,,weird, i know. apparently alot of dirt bike guys run set ups like this. they are 28mm pwks and actually had 125 mains in it before i put in ported reed cages,,,it leaned out a little bit so i went to 128's.and no, the piston did not melt because of this jetting combo either, i did several plug chops to ensure it was jetted correctly and ran this set up for 2 years. the reason the piston melted was because i didnt run my usual half 110 octane,my fault totally. its a stock head shaved .050 and rechambered to 18-19cc and i thought was border line race fuel,i ran straight 93 for 30 minutes and shee melted. any help would be appreciated.