Rotaryphile

I have been rechroming sleeves and lapped pistons since I was in early high school - it is not all that difficult, and the hard chroming equipment only costs a few dollars, although it takes a bit of learning, by practicing on scrap pieces first to get the current and bath temperature right. I have only seen one hard chroming article in model mags, by the venerable C.O. Wright, and it only covers iron pistons, not sleeves, but the principle involved with sleeves is not all that much different. I used to buy worn out, junk engines, and hard chrome them to better than new performance. For doing cylinder sleeves, it is handy to have a lathe available for making up tapered laps, since lapping and honing is essential after chroming, which leaves substantial buildup around port edges, etc. You might get by with a simple brake cylinder hone if you are careful, though. You don't have to strip the old chrome; just clean and acid etch it, and start plating.
The bath is simply chromium trioxide, about 32 ounces per gallon, and about 0.32 ounces concentrated sulphuric acid, in distilled water. You do need a fairly high current DC supply at about 5 or 6 volts, but C or D size nicads will do for small parts, and the bath has to be heated to around 120 to 130 degrees F. The bath is not corrosive - chromium trioxide is a very mild acid, but it will stain your hands and release an aerosol that is not terribly healthy, so good ventilation is necessary.