Nikasil Bores and NOS Cast Iron Rings

[davis]

I don't know if it is common knowledge, certainly wasn't for me, that Nikasil bores need hard rings. Hard chromed steel rings are often recommended for the top ring at least. Bridgestone's rings are cast iron running aroung 23-34 Rc hardness, pretty soft. They will wear quickly on Nikasil which is harder than the original chrome bores. Additionally, they are 2mm thick where modern rings seem only available 1mm thick. Some therefore run two rings in one piston groove - not wild about that. So, I gas nitrided some BS rings to a case depth of .003" -.005", "file hard" which means hard but too shallow to test the Rockwell on. Then I black oxided the rings to gain some lubricity without effecting their physicals.

Also the questions araises, should I use only one ring? It has been mentioned that one ring works just as well below 7,000 rpm and a single ring offers half the possibility of breaking and messing everything up. Just like to hear what you guys think.

[slawsonb]

You raise some good points, Bob. You are certainly creating a solution that will hold up well. I would only offer that since these bikes are likely to see very little use or abuse, the iron rings should suffice for most situations.
...bert

[davis]

Thanks for the input Bert. I would check with Wiseco or Millenium Technologies on expected ring life. They weren't very optimistic.

[bert Lilley]

Hi Bob, well as you know i run 2 1mm rings in myrace setup never had a problem, again if your not racing the stock rings are just fine for everyday runs.

PS i see we have 2 berts on the forum !
Bert Lilley

[BRT-GTR]

           Bob,  RE, Number of rings to use.
        It is my understanding that single ring pistons are used in racing engines to reduce friction losses when trying to maximise power output.   Most if not all of the 350 pistons I've removed show a carbon build up below the rings near the wrist pin ends, so blow by does take place. I'd use two rings for everyday use. I am not aware that ring breakage is a problem on these engines.

[slawsonb]

Hey Bert (pretty good name, huh?...;-). I've been on here for quite a while. Just have been stealthy lately.
...bert (2?)