I have begun to get back in to the hobby after 15 to 20 years.
I am afraid a couple of my OS engines are froze up.
There is no apparent rust and they were kept in a climate controlled area.
I am guessing residual glow fuel oil has congealed.
What's the best way to free them up?
Thanks!
JLK

If the engine has congealed fuel residue, then the easiest thing to do is remove the carb and rear cover and submerge the engine in model fuel. This will dissolve the stuff. Once it's cleaned enough to disassemble, then you can use "four-ought" steel wool and soapy water to clean the parts. Make sure you don't leave any shreds of steel wool in the engine when you're done.