The old 1979 Sachs moped requires a 1:50 oil to gas ratio, which I think would be about 8 ounces of oil mixed with about 3 gallons of gas.
The Mercury Mountaineer still has about 3/4 of a tank, so I was able to siphon out a couple of gallons into a red gas container. The oil I had to borrow from my neighbor, who "loaned" it to me on the condition that he could ride the moped into town next week. Deal.
I don't know much about gas engines, but I'm willing to learn. I found a musty old book in the basement called "Small Gas Engines: how to repair and maintain them" by Paul Weissler, and have been reading it as quickly as I can. Hopefully I won't have to overhaul the engine, but I thought a bit of background couldn't hurt as I tinker and troubleshoot the moped.
A couple of things I have had to fix: a rear flat tire that required a patch on the tube (used a bike tire patch but it seems to be holding); reconnecting the rear break cable; the choke thingy was disconnected from the doohicky so I reconnected it; adjusted the seat to the appropriate level; cleaned up the spark plug; discovered I need to replace a brake light; adjusted the tension on the chain.
After assessing the obvious mechanical problems, I poured a gallon of the precious oil-gas mixture into the moped and miraculously, it started right up! I immediately took it for a spin, driving down the road. About 5 blocks from the house, the thing stopped and wouldn't start. I peddled the thing back home (mopeds truly were not built for peddling) and tried to figure out what was wrong.
Apparently, the fuel filter was clogged by crap from the bottom of the gas tank. I hadn't considered that there may have been 25 year old gas-crud in the tank. I had to remove the fuel valve to drain the tank. My precious gas was completely ruined in the process.
I opened my engine repair book to chapter 7: "Servicing fuel systems." Lots of good stuff in chapter 7, but no advice on cleaning out crud from the gas tank. Unsure exactly how to proceed, simply ran water through the tank to clean it out the best I could. All kinds of black oily crud came out, which I drained into an old milk container. Then I let it dry for a couple of hours, reconnected everything, and poured another gallon of gas-oil mix into it.
This time it did not start right up. I removed the spark plug and poured a tablespoon of gas into it. It fired for a moment, then quite again. After quite an effort, it eventually started, and seems to be running ok now.
I just got back from a five mile pleasure run. It was gratuitous, I know, but so what. A guy's gotta live a little, even a world without oil.
Now I just need to keep the neighbors at bay. I know everyone is going to want to borrow the moped. I think I feel another mechanical problem coming on...