Hi there, just bought myself an elderly 453 with 2400hrs. Gave it a complete service and changed the oil in the chain case. I had to remove the chain case cover because the plug is totally rusted in. Didn't matter much as I wanted to check that all was alright and ensure a proper seal including retapping the treads, (oil was milky...) but now that's all done I would prefer to be able to do normal maintenance, not having to open through the top cover just to check the oil. Any ideas as to how to get the plug out? I tried with WD40 and my airwrench but the 1/2" just went round in the hole. But maybe it's not 1/2"?