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OS .90 fs

Old 11-24-2015, 01:07 PM
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copelab
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Default OS .90 fs

I have an old OS FS-90 that has been sitting in a box for years. Took a look at it an it was completely gummed up and would not turn over. Soaked it overnight an was able to turn it over the next day. However,it seems the pushrods are not moving the valve rockers. What is the best way to approach the dis assembly of this engine. Start by removing the rocker assembly? This is a rear cam 4-stroke by the way.
Bob
Old 11-24-2015, 07:53 PM
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copelab
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My Bad.On further search I found complete tear down and reassembly videos on another site.
Bob
Old 11-28-2015, 11:33 AM
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copelab
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Ok, I took off the rear timing assembly,removed the cam and followers and cleaned it up. Put it back together and did the valve clearances. One thing I did notice is that when flipped backwards the engine had fantastic compression.When flipped in the normal direction the compression was way less. Is this a normal occurrence or do I have something wrong?
Bob
Old 11-30-2015, 07:51 AM
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Bax
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It's normal to have a higher compression feel when turning the engine backwards. Don't worry about it. How the engine actually runs is what is important.
Old 12-02-2015, 01:22 PM
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copelab
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Finally ran the engine for the first time since 1994. Just put one tank through at a little above 8000rpm. Used a 13-6 prop an Omega 15% fuel.
Bob

Last edited by copelab; 12-02-2015 at 02:05 PM.
Old 12-30-2015, 05:16 PM
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Hey Bob, I've got the same engine. I need a cylinder head, half of the muffler threads broke off. Do you know if there's one available anywhere? I don't want to run it without a muffler. Brian
Old 12-31-2015, 07:22 AM
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Only an internet search or a query posted in the general Engines forum would get any results.

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