I own a Zenoah G38 and have it installeld in my Giant Aeromaster. The engine is performing adequately but not at peak performance. Today I pulled the spark plug after using it for about 80 minutes of total flight time. The plug was blackened, wet with a layer of oil and had a coating of carbon over the entire plug tip. I have been using 87 octane fuel with 10 percent ethanol plus a 32 to one ratio up till the last two flights. These flights used 87 octane and a 50:1 Bel Ray mix.
Am I running too rich? What should a good plug look like? Looking for guidance based on experience. Thanks.

yes, your rich. plug should be a light tan colour. just google spark plug reading

theres plenty out there
http://www.theultralightplace.com/sparkplugs.htm