Sorry Jan but I completely disagree here. Castor is a marvellous preservative and even after it's gone all gummy over many years it's still preserving the bearings. However, the gummy feel can make it seem like the bearings are rusted where in fact it's just tiny balls of gum making the bearings feel graunchy. Filling the crankcase with fuel and working the crankshaft around can slowly dissolve the gum but I prefer to take the bearings out and give them a good clean.

For an engine that's hard to start when there doesn't appear to be anything wrong (plug works fine, it's got compression, no junk in the needle valves etc) the first thing I do is to open the main needle so I know it's very rich, give it a reasonable prime then start it at full throttle. That eliminates any problem with the idle setting. With the glow ignitor connected an engine will keep running extremely rich so you have plenty of time to lean it out to a better mixture before going back towards idle to check that setting.