7. CYLINDER/PISTON K-XCT 125i TROUBLESHOOTING When hard starting or poor performance at low speed occurs, check the crankcase breather for white smoke. If white smoke is found, it means that the piston rings are worn, stuck or broken. Compression too low or uneven compression Excessive smoke from exhaust muffler Worn or damaged cylinder and piston rings Worn or damaged piston rings Worn, stuck or broken piston rings Worn or damaged cylinder and piston Compression too high Abnormal noisy piston Excessive carbon build-up in combustion Worn cylinder, piston and piston rings chamber or on piston head Worn piston pin hole and piston pin Incorrectly installed piston 7-3