40 fs, info on ring/cylinder
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40 fs, info on ring/cylinder
the 40 fs i have (circa 1990), was hardly run, the ring and cylinder look almost perfect (of course the bearings are junk). the ring is nice and clean, doesn't appear to be warped, the cylinder looks real smooth, with more than a dozen barely visible verticle scratches. i only intended to replace these because i wanted to get all the power possible out of the engine and make it like new. is it worth replacing either? i read on a post that the cylinder could be honed w/a brake hone, with a couple gentle turns. i got three bearings out (using a torch, as recommended by harry higley book), but the cam bearing in the case is absolutely stuck, i have heated and banged it, nothing. in the book, he shows holding the case in his hand, but it doesn't work that easy for me. i'm afraid, i heated the case too much. i figure if the ring and cylinder don't need to be replaced, that would off set the cost of a new case (tower $39), is this the same case, even though mine is 16 yrs old? i have new bearings on the way, so, i would like to finish this.
jon b
jon b
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RE: 40 fs, info on ring/cylinder
It's hard to say, but if the scratches are small, then they'll be nothing to worry about. The total compression of the engine is the important thing. How does the engine run at full throttle when propped and leaned correctly? It should turn in the mid to high 9,000's. If it's the Surpass version, then perhaps a bit more...into the low 10's.
The interior cam bearing usually needs to be extracted with a puller. People have made them with small headed nails filed to fit into the center of the bearing, and then expanded with a small wedge. The nails are clamped together in a hole drilled into the end of a piece of steel dowel, and then the dowel is used like a slide hammer to extract the bearing after the case is heated. There is no commercially-available tool available to do this. They are all home-made. See Harry Higley's book, "All About Engines" for details on the tool he made.
The interior cam bearing usually needs to be extracted with a puller. People have made them with small headed nails filed to fit into the center of the bearing, and then expanded with a small wedge. The nails are clamped together in a hole drilled into the end of a piece of steel dowel, and then the dowel is used like a slide hammer to extract the bearing after the case is heated. There is no commercially-available tool available to do this. They are all home-made. See Harry Higley's book, "All About Engines" for details on the tool he made.