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Discussion
Super Tigre S25
I picked this engine up this week with the intent of replacing an ST S29 Ring engine and using a tuned pipe for a speed application. The seller said it was ABC - which seems mostly true. It is a ringless design, but the liner is plated inside and out. I have several other SuperTigre/Como ABC Engines and none of them have chrome on the outside of the liner like this .25. It’s an old stock engine given the fact it uses a bolt-on muffler. My S29 uses a boot-through muffler mounting. My question is whether Super Tigre fully chrome plated the inside and outside of the liner on some of their engines or if they dabbled with nickel plating at all? The bore has been ground, so I suspect it is indeed chrome since nickel doesn’t require a post-plating grinding of the bore.
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I Always thought, there were technical reasons for chrome plated liners to be not plated inside and out....
Can it be that the liner is not made out of Bronze, but is chromed steel, in which case it is hard to see whether the coating is only in the bore? Because I believe, chrome plating has to be ground to be true to size so you would have to see some form of grinding on the outside as well if it were chrome all around. (just going from memory, I could be very wrong....) |
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The liner nor piston is magnetic. Also, Ferrous liners wouldn’t work with aluminum pistons due to the difference in expansion rates of the two metals. The liner in this engine has a fairly snug taper, which is not something I’ve seen in Nickel plated liners. Given the grinding inside the bore, I expect it to be hard chrome, I just haven’t seen an ST liner plated this way.
There is no evidence of this engine ever having been mounted and certainly not run, so I don’t think someone stuffed replacement parts into it or anything like that. It’s too bad there isn’t more information about some of the S-series ST engines. I haven’t found squat about the .25 yet. I guess they made a S .36 as well that was a very limited production engine. I think it was made for combat or something like that. I believe the S21 through the S36 all used the same crankcase. |
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I think the method of plating has more to do with the results, than the material used to build it up. There is masking as well. A thick coating will round over and build up on corners and edges, which needs to be honed or lapped away. A thin even coating is what is normally used with the nickel, but I am not sure what would happen with the same process in hard chrome. Either way, I would still run it until it wears out, and not concern myself about it.
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Typically one will see some chrome fade on the edges of the ports, but I haven’t seen a brass liner with chrome on the outside yet. This is likely the first for me as I do not believe ST ever used Nickel. They did pioneer the true ABC construction method after all.
Aspeed - I intend to run this engine without much worry. It will likely outlast me on this earth. I would just be a little hesitant running it real hard on a tuned pipe if it had a nickel liner. |
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The shiny cylinder is chromed, the dull one is Nikasil. Big difference in appearance. Chromed liner is silky smooth, Nikasil is not as slick. Just saying.
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Super Tigre never used Nickel or Nikasil that I’m aware of - and I’ve been searching for the last 3 days. If you have some factual information to share to confirm what it is, then that would be helpful. Pictures don’t really prove much.
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Last edited by 1QwkSport2.5r; Jan 31, 2018 at 09:23 AM.
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Use an NDT method, take scrubbing bubbles cleaner, soak a cotton ball and rub the outside of the liner. If the cotton ball starts to turn pink, it is nickel plated. The cleaner contains N-alkyl dimethyl benzyl ammonium chlorides. it reacts to any type of nickel plating.
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Quote:
thanks Michael in Ontario, Canada |
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Here it is. It's by SC Johnson
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I haven’t had a chance to see if I have any SC Johnson Scrubbing Bubbles around the house, but I put some Neodymium magnets to the piston and liner of this ST S25. Because the gudgeon pin was still in the piston, the magnet was mildly attracted to the piston. There was virtually NO attraction to the liner. As I understand, Nickel is wholly magnetic and chrome in and of itself isn’t magnetic, however other metals alloyed with chrome can make it magnetic. So I believe the liner in this S25 is hard chromed inside and out.
There is currently an ST S25 buggy engine for sale on EBay that clearly shows the top of the liner beneath the heatsink head and brass is clearly visible. So I’m a little confused as to the difference between an s25 aero and an s25 buggy engine. |
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