My bike seems to have developed a cackling [mild backfire] when i back off down through the gears. Acasionally it overheats in the tight stuff but today it overheated very easily in not so tight stuff. Seemed ok after i rode it home although still cackling. The bike has 3000k's on it. Bought new uncorked with the power up kit installed. Always starts easy. I have heard on this forum that the pilot jet may be too lean. Why would this problem develop and not from new. Any takers?