Re: 530 vs. 540 Engine and Tranny Debate (archive)

I had several Moto Guzzi motorcycles which had hard-chromed bores, no liners. I had no problems with either bikes related to the cylinders, however, at about 40k miles, the chrome wore through on the thrust side of the piston at the top of the stroke. I ran it for another 20k when I sold it, while keeping an eye on it during routine maintenance. Nikasil is similar, in that it is applied directly to the aluminum cylinder wall. For me the issue is with how a failure can occur. Moto Guzzi claimed that by having no liner, the aluminum cylinder and aluminum piston expanded at closer rates and could be manufactured and operated with tighter tolerances which reduces noice, oil consumption, and other things.

With two wheels under me, I worried what would happen if the cylinder/piston/rings failed catastrophically. I'm sure I'd go down hard, hopefully not at speed on a freeway during heavy traffic. In a car, the failure would be less dramatic, tho more expensive. With a coating like chrome or Nikasil, if it comes off (say a ring breaks and starts scoring the cylinder wall), before you know it these very hard materials are strewn all over the guts of the engine and probably would destroy every bearing surface. With a liner, however, I would expect damaged to be much less severe and localized if caught in time. The coatings on aluminum would probably go very quickly and catastrophically by comparison.

My opinion, I like liners. I think they give me just a little more security in my engine, whereas coated cylinder walls probably last a long time until they fail with great fanfare.

Don

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