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Valve Control
As suggested in the engine manual under “Daily Checks” turn the prop to check engine/ valve condition. There have been many instances over the years with engines either being returned for maintenance or overhaul where if this simple task is done, valve seal rectification work would be required to a lesser degree. When poor valve to seat condition is allowed to go on unchecked eventually valve distortion and eventual failure could result. When good pre-flight and maintenance procedures are carried out a better standard of aircraft and pilot would follow. There are 50 hours between inspections and the “daily” should be treated with all the seriousness and respect it deserves. Be especially on the look out for a weak valve seal on the “daily”. This is something, while not very common, is often overlooked. We've seen an older engine that had 2 exhaust valves distorted and obviously not sealing. This had gone on for a fair period of time. Poor valve seal can result from “normal” operation with rubbish infiltrating the valve seal area. Mostly by the engine operation this material can be dislodged. Operating the engine outside recommended CHT’s, incorrect valve clearances, fuel standard and type, blown exhaust gaskets, lean running etc, can all contribute to build up and leakage in this area. Valve clearances should be adjusted in accordance with the maintenance manual. Remember preventative maintenance is much better than maintenance repairs. In Australia they now have tens of thousands of hours with some flying schools having operated Jabiru aircraft for 4000-5000 hours and beyond. To date we have something in the vicinity of 500 engines sold in the UK as of November 2004.
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