How do you check for cylinder head warpage, and what is the typical service limit for flatness on a small motorcycle engine?

1. Place a precision straightedge across the head surface in diagonal directions and measure gaps with a feeler gauge; the limit is typically 0.05 mm.
2. Inspect the head visually under a magnifying glass; if no cracks are visible, it is flat.
3. Measure the thickness of the cylinder head at the four corners using a vernier caliper; the limit is 1.0 mm.
4. Roll the cylinder head on a flat wooden workbench and listen for wobbling noises.