http://www.blasterforum.com/engine-13/cylinder-porting-diy-25773/ General Basics of porting, even though it shows a Blaster cyl., its basically the same. The trick is HOW MUCH to raise port roofs. Because of languge differences , do I understand you correctly that your cylinders can NOT be bored out any more? If that is the case , a clean up certainly will not hurt. A lot of information to read AND understand before you go crazy with a grinder. Also, just wondering, are you typing in English , or are you using an Arabic / English translation program? Hope this helps , post back if you have more questions.