Cylinder – Nikasil Coating; Recoated Cylinder - KTM 400-660 LC4 1998-2005 Repair Manual

5-9E
Cylinder – nikasil coating
Nikasil is the brand name for a cylinder coating process, developed by
the piston manufacturer Mahle. The name is derived from the two
materials used in this process - a nickel layer into which the particularly
hard silicon carbide is embedded. The main advantages of the Nikasil
coating are excellent heat dissipation and thus better power output, low
wear and low weight of the cylinder. The worn coating can be
regenerated at low cost provided that the running surface of cylinder is
flawless.

Recoated cylinder

If the Nikasil coating of your cylinder is worn but undamaged, you may
obtain a recoated cylinder at your KTM dealer (new Nikasil coating on
used cylinder).
It may be that your spare cylinder shows color changes on the exterior
side.