Usually with these old two strokes all that is needed is a new glow plug and a heat gun to loosen them up. The old castor oil gunks up in them but once heated so they will roll over they will usually fire up again. With the bearing engines if you like you can open them up and clean them completely. If it's a really good engine I will take the time and do that. Something like an OS 1.08, I usually don't bother with the smaller engines.