My engine came today, and even thought the ebay seller is a liar of monumental proportions, I was ready for him sorta. It took four hours but I got the engine through phase one. Rryobi 31cc engine instructions.
I am not going into all I had to do to make the engine run. Lets hope you score one that is already running. So lets begin at that point.
If it is on a trimmer you need to deconstruct it.
This is the first step.
1. Remove the steel shaft leading to the line feed head. Usually there are four screws holding it on. Just take them out and it should come right off.
2. With that removed, you will see a silver bell shaped piece. That is the outside cover of the centrifugal clutch. At the end of that hollow tube is a screw which holds the bell onto the drive shaft. To remove it you need to block the drive mechanism of the engine. To do that remove the spark plug and stuff a rope into the spark plug hole. Be sure to leave some of the rope sticking out so that you can remove it.
use a flat blade screw drive that will fit into the hollow tube to remove the screw. It should be easy enough to remove. Since you have blocked the engines ability to turn over it should work no problem.
3. Now that the bell is gone you should see the real clutch parts. There are a couple of springs. If you remove them the clutch will fall apart. When it does it leaves a jam nut with what looks like wings. Just take a vise grip and unscrew it. Now you have the first phase done.
This is how your engine should look at this point. The bolt I added it is a 3/8" fine thead cruiser axle bolt. YOU can use a bmx axle peg (not mountain bike) as a drive wheel. I am going to use something different and that bolt will hold it on (I hope)