With bore scoring a concern for most owners, customers can become hypersensitive to the issue and find a problem where one does not exist. Nikasil is a very hard and durable nickel silicon carbide wear surface electroplated onto the cylinder bore. It's important to point out that Nikasil does not suffer scoring like Alusil or Lokasil.
When bore scoping a fresh engine, what you are seeing can be commonly misdiagnosed as scoring when it is in fact streaking. Streaking, as shown in the photos provided to us by Millennium Technologies (who does our NSC plating for our Nickies cylinders and sleeves), is nothing to be concerned about.
Millennium Technologies states that "a certain amount of streaking is normal during break in as the rings and the coating wear into each other. The marks are lot like tire marks on pavement and need some time to wear off. More time on the engine in most cases will help ring seal. The extra time will not damage the coating further."
It is completely normal to experience streaking caused by transfer during break in of piston and ring coatings. During the break in process, streaking is analogous to a "footprint" left behind from the rings, piston coatings, and Nikasil while they all mesh together and is cosmetic, not affecting ring seal or engine performance. Given time, streaking will dissipate with continued normal usage.
To ensure the best possible results from your engine rebuild and minimize the appearance of streaking, it's important that a few critical steps are carried out:

  • Cylinders must be properly cleaned using Kimwipes and denatured alcohol. The residual honing oil/Nikasil mix on the cylinder bores is very abrasive and will cause damage to the pistons, rings, and cylinders if not cleaned. This is the most important step!
  • Do not install pistons and rings dry. Unlike cast iron cylinders, engines with Nikasil or NSC-plated bores require lubrication. Improper assembly using the wrong lubricant or none at all will increase streaking and also cause accelerated component wear.
  • The engine should be broken in using conventional (non-synthetic) break-in oil and under no circumstances should any oil be used containing moly or other friction modifiers. Use of additives, partial, or full synthetic oils will lead to cylinder bore glazing and poor ring seal, requiring the cylinders to be de-glazed and pistons re-ringed.
  • The next most critical step overlooked is the fuel system. With today's ethanol enriched fuels, components like fuel injectors and fuel pumps aren't lasting as long as they used to. It's important to pump out all the old fuel (older than one month), replace the fuel filter and injectors, and verify fuel pressures and volumes. Bad injectors can cause poor fuel stray and leaking injectors can wash down cylinder bores, resulting in damage to the pistons, rings, and cylinders.
  • When fitting the intake, seals and gaskets must be replaced and the engine should be smoke tested to verify there are no vacuum leaks. Vacuum leaks can lead to over-fueling that again will damage your fresh engine, resulting in a teardown to repair the damage.
  • Last, but not least, sensors like the MAF (mass air flow sensor) and o2 (oxygen sensors) should be replaced to ensure the ECU can properly meter air and deliver the right amount of fuel. Dirty or old sensors will default to rich and again cause poor operation and engine damage. Overlooking these critical items can lead to costly mistakes, but they are easily avoidable. 
Be sure to download our bulletins prior to engine assembly, installation, and break-in the ensure the best possible outcome for your air-cooled or water-cooled engine rebuild:

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