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Jan 19, 2019, 07:01 PM
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Stuck valves on Saito FA-72


Anyone have recommendations on how to easily free stuck valves on a Saito 4 stroke, without damaging the spring/valve? Engine hasn't been run in a few years, but has a low run time. Was thinking of locally heating the area and prying the spring up with a thin screwdriver.
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Jan 19, 2019, 07:28 PM
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Soak or heat should free it up, Most likely congealed castor causing the problem. Don't force it as you may cause damage. I use 91% rubbing alcohol to soak for an hour or so and then heat.

Regards
Dennis
Jan 19, 2019, 08:35 PM
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Thanks Dennis, I will give that a try.
Jan 19, 2019, 08:57 PM
Club Saito | Genesis 8:11
Bunnyshooter223's Avatar

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Heat and oil, i assume. I have one of those heat guns, you know for shrinking the wrap on rc airplanes. It actually gets plenty hot! I use it to remove bearings, so i think it'll work

In fact, i just used the 'heat gun and oil method' to remove a stuck front bearing. A wrench extension and mallet (actually small light hammer in this case) will knock them out (metal punch on the bearing is not too much an issue because it will be discarded)

Dont use metal-on-metal otherwise--the screwdriver prying valves might end up in damaged valves. Maybe a piece of wood pushed against the the valves would be better? with heat and oil of course

Btw the congealed castor is said to prevent rust. It may seem a mess but congealed castor is better than rust. If pilot would run the engine out of fuel and use oil there may not be stuck valves. These days many pilots seem to use synthetic/castor mix to keep things cleaner.
Some say Castor is best for the valves...
Last edited by Bunnyshooter223; Jan 19, 2019 at 10:47 PM. Reason: *said typo
Jan 19, 2019, 09:55 PM
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Thanks for the additional suggestions!
Jan 19, 2019, 10:49 PM
Club Saito | Genesis 8:11
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yes you are welcome
Jan 20, 2019, 03:34 AM
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Quote:
Originally Posted by Bunnyshooter223

Btw the congealed castor is said to prevent rust. It may seem a mess but congealed castor is better than rust. If pilot would run the engine out of fuel and use oil there may not be stuck valves. These days many pilots seem to use synthetic/castor mix to keep things cleaner.
Some say Castor is best for the valves...
True, congealed castor is better than rust, and true, the congealed castor seems to be an excellent rustpreventer....
But not sticking valves and no rust are even better…. Simply because every time an engine is stuck, it is in imminent danger of being damaged by inexperienced people trying to un-stick them…. Better to prevent sticking, IMHO
Jan 20, 2019, 05:20 AM
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Dried castor does protect parts from rust/corrosion and that is a good thing. Avoiding using fuel with castor in it is one way to stop this and then subject the engine to actual rust by using synthetic oil only fuel. The BEST thing is a blend of castor and synthetic and a PROPER shutdown of the engine. Proper after run oil use for long term storage is also recommended if this is stickiness is considered to be undesirable.

However I would rather buy an engine that is stuck/sticky due to dried castor than due to rust/corrosion. The knowledge in how to deal with such a situation, oil/heat, is far less restrictive than limiting the types of fuel the engine can use.
Jan 20, 2019, 08:11 AM
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I TOBOR's Avatar
I use a combination of zero castor and Corrosion X after run oil, it works. I installed 18" of fuel tube on the CX spray pump and pump the CX right into the vent.
Jan 20, 2019, 08:38 AM
No spark, no waste.
Gary Cee's Avatar
You can have the best of both worlds very easily. It does not take a lot of castor to get the benefits, without the varnish problem that some have.

I have been running 12% synthetic and between 2% and 4% castor. Varnish is not a problem, nor rust.


Klotz rates the anti wear quality of their synthetic/castor blend at 20% better than their straight synthetic .A desirable quality.

No rust, no sticking valves. BTW rust can and does cause valve sticking at times Seen straight synthetic oiled engines with
valves stuck.
Last edited by Gary Cee; Jan 20, 2019 at 09:02 AM.
Jan 20, 2019, 09:58 AM
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This is all very useful information. Thank you.
I was told by the person who sold me the engine that after run oil was used, and the carb barrel did move freely, but there was no compression, so I knew it had a stuck valve(s). What always surprises me in this instance is that upon removal of the valve covers, there is always ample oil around the rockers/springs (I guess that is "blow-by"), but the valves are sticking, presumably from congealed castor where the valve stem penetrates the head.
Jan 20, 2019, 10:10 AM
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Quote:
Originally Posted by Sdeminco
but the valves are sticking, presumably from congealed castor where the valve stem penetrates the head.
Not really… the castor congeals first on the parts that get really hot during operation, and expecially the exhaust valve gets pretty hot...
Jan 20, 2019, 10:24 AM
No spark, no waste.
Gary Cee's Avatar
Using the correct amount and with ARO, sticking from castor is not a problem. Four strokes only here for decades. Sticking valves is no problem.
Latest blog entry: Responsible fliers.
Jan 20, 2019, 04:31 PM
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I like to pull the fuel line of and let the engine run dry . I then use a marine grade of fogging spray into the engine , then restart with starter and battery . The engine will fire on the fogging spray . Works good on marine engines around water why not use it on our aero engines . Works for me ...

Mike1484
Jan 20, 2019, 06:49 PM
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Thanks guys for all the good advice. As recommended I soaked the engine head down in a cup of 91% alcohol for a couple of hours. (I first cleaned the outside of the engine, then removed the muffler, glow plug, and rocker covers.) After thoroughly draining the alcohol I applied some after run oil around the rockers, and into the intake and exhaust ports. I heated the head area with a heat gun for several minutes, then carefully applied some upward pressure on the valve springs with a very small screwdriver, being careful to not damage the spring/valve assembly. As expected, the intake valve freed up first, then the exhaust valve. I had to push down on the valve with a wooden dowel and cycle the valve up and down to work the oil around the valve stem. Both valves now move up and down freely, and the engine has great compression. SUCCESS,!


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