Skip to content
Custom engine and cylinder head work for a motorcycle

Cylinder Head Service

With years of porting and cylinder head repair experience behind us, we can handle all of your needs. We have a modern machine shop, equipped with the latest, most advanced tools and equipment to modify your cylinder head—for car or motorcycle; street or track; multi, twin, or single cylinder. From copper based seat replacement for titanium to fully radiused seats. Metric Motorcycles is full service.

To give you some idea of what is involved when we modify or repair your cylinder head, we will walk you through an overview of the process we follow for every cylinder head:

  1. We assess the general condition of head. We take accurate measurements of:
    • the camshaft bearing clearance
    • the bucket bores to make sure they are not damaged
    • the spark plug hole
  2. Clean heads and prepare for guide removal and installation.
  3. Remove old guides and install new guides, heating the head up to 280 deg to aid the process.
  4. Guides are reamed or honed to size. I like to run 0.0015 to 0.0030 clearances. The head is now ready to have its seats machined.
  5. Seats are machined on a T&S Seat and Guide Center, using very precise carbide form tools. The form tools are designed by me and made by Newen to my specifications. The science behind it is rather complex. The only sure thing is the valve seat angle is 45 degrees. The width and corresponding angles and radii are up to the tuner. I must admit that we’ve borrowed greatly from a certain Italian race team’s 4 valve specs.
  6. Machine work gets complete and all valves get seated in to the head at exactly the same depths. This ensures perfect even compression ratios and ultra precise work.
  7. Heads are then sent to a metric PCBN fly cutting system. This tool helps me maintain accuracy on the amount of material being removed. Both of these heads will be “CC’d” so that we can calculate the compression ratio.
  8. Chamfer all the hard edges around stud holes and water jackets. The head the receives a thorough cleaning. I actually wash them with hot water and soap. Miniature brushes are used to scrub each valve guide.
  9. Cleaned, it’s ready for new valve guide seals and final reassembly.