I bought an old OS engine which seems to have not been used for some time. The engine does not seem to be damaged as it does have compression. From the exhaust port I can see that the piston does have some brown stuff on it which I am guessing is the castor. Should I try to take it apart and then clean it or should I try to get some fuel into it and hope that it will get rid of the castor.
Some browning of the piston is normal in high time engines regardless of what oil is used. The hotter the engine is run, the more brown there will be. It is usually not harmful unless it builds up too much on the top of the pistont and affects compression.
If the engine turns over smoothly and has compression, don't take it apart. Run it with some sport fuel containing mostly synthetic oil with a smaller amount of castor. Any excess carbon will be dissolved by the synthetic oil while running.
Unless the engine is really gummy and stiff to turn, leave it alone. Start it and let the new fuel and heat clean any old deposits. Dr.1 Driver "There's a Hun in the sun!"
Don't clean the insides of the engine unless it just won't run, and even then it might not have a positive effect.
To clean the gunk off of the outside I use Easy-Off oven cleaner.
Good luck Greg
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