Manual - Chapter 1 Engine

18. Examination and renovation: cylinder head

  1. Remove all traces of carbon from the cylinder head using a blunt ended scraper (the round end of an old steel rule will do). Finish by polishing with metal polish to give a smooth, shiny surface.
  2. Check the condition of the spark plug threads. If the threads are worn or crossed they can be reclaimed by a Helicoil insert. Most motorcycle dealers operate this service which is very simple, cheap and effective.
  3. Lay the cylinder head on a sheet of 1/4 inch plate glass to check for distortion. Aluminium alloy cylinder heads distort very easily, especially if the cylinder head bolts are tightened down unevenly. If the amount of distortion is only slight, it is permissible to rub the head down until it is flat once again by wrapping a sheet of very fine emery cloth around the plate glass base and rubbing with a rotary motion.
  4. If the cylinder head is distorted badly (one way of determining this is if the cylinder head gasket has a tendency to keep blowing), the head will have to be machined by a competent engineer experienced in this type of work. This will, of course, raise the compression of the engine, and if too much is removed can adversely affect the performance of the engine as well as to cause the valves to strike the pistons. If there is risk of this happening, the only remedy is a new replacement cylinder head.
  5. Refer to Section 17 and Section 19 of this Chapter for details of work concerning the camshaft bearings and valve gear respectively.

The history of BMW

1928 - Engine R63