Author Topic: centaur gas engine  (Read 1902 times)

Offline Frank Boyle

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centaur gas engine
« on: July 27, 2016, 08:18:27 PM »
Having completed the engine I have had trouble with sealing the valves,but after many hours of grinding I have got them seated.With the carburretor off and covering the ports I have compression,but with the carburretor on I loose compression.I have ground the valve in but I think that the spring is not strong enough and the valve is lifting on the compression stroke and air is exhausting through the air intake.Is a stronger spring the answer or any sugestion will be welcome.
Frank

Offline Rustkolector

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Re: centaur gas engine
« Reply #1 on: July 28, 2016, 12:25:18 AM »
Frank
I'm not familiar with the Centaur head design, but leaking valves are often a problem. Continued lapping of the valve seats generally will not help if the valve seat is not concentric with the valve guide. Heavy lapping or grinding will deform the seat and valve face. You should not feel any compression pressure at the intake or exhaust ports if the valves are seating properly. On the compression stroke, any pressure felt at either the intake or exhaust port openings indicates leaking valve seats. There was a previous Centaur build post on this website. You might want to contact that builder for assistance.
Jeff

http://www.modelenginemaker.com/index.php/topic,3699.0.html

Offline Frank Boyle

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Re: centaur gas engine
« Reply #2 on: July 28, 2016, 05:01:09 PM »
Thank you for your reply,I have worked on the valve cage and checked it's seating with marking blue I also slipped an 'o' ring on the bottom.I am sure the cage is now sound.I am taking another go at seating the valve but doing it in situ as I think that you are correct and the spindle may not be true with the valve seat.
Frank

 

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