I have a Honda Gold Wing that is a model year with known susceptability of the dashboard display circuit board to moisture. High humidity and rain cause anomalous behavior on the LCD. Other Gold Wing owners report that the way to stop the problems is to remove the circuit board, clean it and coat the backside with silicone to prevent moisture.

Are there cleaning and moisture selant products anyone would recommend for this job?

 

Use isopropyl alcohol and an acid brush to clean the board thoroughly.
You can get 99% isopropyl alcohol at hardware stores. Don't use the 70% isopropyl or "witch hazel" from drugstores as there is too much water in it.
You can usually get the acid brushes (black nylon bristles, rolled metal handles) at auto parts stores or hardware stores.

If there is any corrosion evident (usually looks white/powdery) remove it using hand sanitizer and a worn toothbrush, then follow up with isopropyl alcohol. Allow the board to dry completely.

Most RTV silicone you buy in stores emits ascetic acid during curing (which is corrosive), so it's not good to use on electronics.

You can use a clear acrylic spray lacquer as a conformal coat to seal the board. Use several light coats; heavy coat will take a long time to dry.
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Cover with tape any board connectors that might otherwise be sprayed. Use an automotive-grade silicone connector lubricant (it comes in tubes) to seal out moisture and dirt.

 

Also, remember to do this with the power off.

The coating process can cause a short, and possibly a spark which can cause the flammable solvents in the coating to ignite.

I know you said you would remove the board, but remove and disconnect are 2 different things.

 

Another vote here for using an acrylic spray in several light coats.

Stay away from tubes of RTV silicone.

If desperate, and you have it on hand, Shellac can be used, but it is brittle and vibration will cause it to crack eventually.

Urethane varnish will not adhere properly to the slick fiberglass surface and will not seal the board for very long. It will actually trap moisture.

 

Stay away from tubes of RTV silicone.

I think our OP is referring to the spray silicone, which is a completely different product. Still, it is probably not the best product for this application as it is a temporary preventative, never really dries, and can collect dust & dirt.

I add another vote to the acrylic lacquer solution.