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Dec 14, 2013, 02:02 PM
Cat Man
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OS FS 90's

I now have (2) os FS-90 4 stroke engines. I just recently purchased my second one from a member here for a very good price, well under $100. It is just the engine, no box, paperwork or tools.

When it arrived it would not even turn over. The seller did not think there had been much run time on the engine but let me know the condition. As I always do with used engine purchases, I completely disassembled it. It had been run but by the looks of it not more than a few tanks. It was gummed up from the fuel/oil residue hardening inside.

I cleaned it up and very thoroughly and had it on the bench today. Just as my other FS-90 it started on the first flip. Soon it was turning a 14x6 at 8500 RPM. It would turn it more than that but this is usually where I set my 4 strokes while on the bench.

Now I have 2 very nice running FS-90's and no planes for them.
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Dec 20, 2013, 09:21 PM
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Cougar429's Avatar
What do you use to clean your engines? I use the crockpot/glycol for really gummed up engines and normally go with new bearings if apart.
Dec 21, 2013, 07:46 AM
Cat Man
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I ususally soak stuck or gummed up parts in standard isopropyl alcohol for as long as necessary. I also use old tooth brushes to scrub and clean the exterior. Many paper towels to wipe and clean the internals. For the surface rust on steel parts and bearings I soak in CLR. Once done in CLR I soak/rinse thoroughly with more alcohol. Once everything is clean I lubricate with either a small amount of 3-in-1 oil or Marvel Mystery Oil.

I don't replace bearings unless absolutely necessary. After the CLR treatment I can tell if they need to be replaced. If gaskets are bad or damaged I seal with Permatex MotoSeal 1 ultimate grey gasket maker.
Thank you for you inquiry.
Dec 21, 2013, 09:06 AM
Registered User
Cougar429's Avatar
Thanks for the info.

With engines I grab at swap meets and such I find most are cases of lack of knowledge in setup and after run treatment. The parts are in good condition, but corrosion has taken out the bearings, (the sole reason I replace them). The other ferrous bits can be easily cleaned up and as mentioned, the rest goes into the hot bath. Methanol is the final cleaning agent, but the hot glycol will usually have all the parts, (or an entire engine) shiny in little over 30 minutes.

I had one of those 90's years ago. The numbers you posted are pretty good.

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