Hi,
There are many ways to clean a motor ranging from an ultra sonic bath at a hydraulic specalist, a tooth brush elbow grease and solvent or the crock pot method. I've used them all with various degrees of success and satisfaction however if you wish to restore the shine of a new motor the only method I've found that gives fantastic results is soda blasting. The metal shines like new and with a coat of engine clear from the auto parts store will retain its' lustre for years. Do a search on soda blasters in your area on the net or the phone book, the cost is minimal if the motor is disassembled and the results are well worth the few dollars IMHO
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Cheers,
Colin