Pre-unit twin with gearbox that bolted to the back of the engine and dry sump cast into its bottom, post ’58 Meteor Minor much superior to milder, long stroke earlier model. The Minor still leaks a little bit of oil, has queasy handling flat out and can do nasty things to its crank’s bearings if pushed to the limit, but under sensible use it’s close to being the best of the 500’s. They are rather rare but worth tracking down.