bertie Posted May 9, 2009 Share Posted May 9, 2009 I have a new to me but used SC30FS in very tidy condition. I am however puzzled by its lack of compression, or low compression. I have tried to hand start it, but no luck. Tickle it with an electric starter and she is away, as sweet as a nut. Good throttling, good top end (10500rpm on a 10 x 4) and sweet idle. I may be worrying unecessarily, but the engine just doesn't feel right with no, or very low compression! Any one out there with a similar experience? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted May 9, 2009 Share Posted May 9, 2009 hello bertie-i'm no expert-i own a couple of 4st's-if it run's ok-that's all you want-if you really think there's something not right-take off the rocker cover and check the tappet clearence...ok...that's it run and enjoyo..................10.500/sweet idle what more could you want.................... ken anderson.............. Quote Link to comment Share on other sites More sharing options...
Mark Lubbock Posted May 9, 2009 Share Posted May 9, 2009 Is it a ringed engine? they somtimes feel as compression is low when turned by hand, particularly when new. As the others say, if it runs well all islikely to be OK. It may be worth checking there is some valve (tappet) clearance to be safe. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted May 9, 2009 Share Posted May 9, 2009 Mark Yes I think its ringed the others in the range are/ I would say its not fully run - in Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 9, 2009 Share Posted May 9, 2009 Bertie Just how little compression? Small 4 strokes can suffer from specs of carbon getting under the valve seats preventing an air tight seal but do check the tappet clearances as well. If you can get the engine running at all it will probably clear itself and the compression will return. If it doesn't, then some work will be required. Quote Link to comment Share on other sites More sharing options...
bertie Posted May 10, 2009 Author Share Posted May 10, 2009 Many thanks for the replies. The engine is now installed in a model and I have run it up okay. Still very little compression, but starts okay on my electric starter, and seems to run fine. The tappits are loose (I used an O.S. set of feeler gauges which came with my first generation O.S. 40 FS years ago). So I will use the engine and see what happens! Happy flying, and thanks once again Bertie Quote Link to comment Share on other sites More sharing options...
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