Scrub potatoes; boil in boiling salted water until tender. Drain and while hot skin and cut into ¼ inch slices; sprinkle with the salt, pepper, sugar and flour. Add water to vinegar and let heat thoroughly. Place bacon in spider, let fry light brown, add onion, brown slightly, add potatoes and over all pour the hot vinegar, let heat through to absorb the vinegar and water, place in serving dish and serve hot. The bits of fried bacon may be omitted. If the salad is too dry add a little hot water. It should have a glassy look, without being lumpy or greasy.