Tried my conversion out yesterday. I made a prop hub out of a deep well socket. It worked but added some weight so I got a aluminum one coming from wackerengines. I slotted the needles and that worked great. Made the mount out of ply and its attached with the four back plate screws (which I had to replace with longer ones). For the throttle I used a nose wheel arm from a trike gear setup. Just drilled out the bushing to the correct size. Worked great. Mine has the 5/16 shaft so I was able to use the same prop nuts that fit four stroke glow engines. This was mounted on my GP 60 size Tigermoth and put in a 14oz tank. Weight on the box shows the TM coming out at 10.3 lbs. With the 25cc engine it came in at 11lbs even. So not too bad. I did have to cut a slot in the tail and mount my receiver battery way back to balance.

Got to the field and no one was there since it rained part of the day. I prefer to beta test planes with no one around anyway (for safety and humility). Fired up the engine and could get it to idle down. Turns out I had the linkage set wrong. After pulling the clicker the butterfly will turn 180 degrees. Apparently it really only functions properly one way. So a quick reverving of the channel and a turn of the phillips fixed that. Tried to tune it a little. Seemed like when I leaned it out I was only getting about 6400 rpm on the master airscrew 16x8. That was when the engine went from the fourstoking sound to a smooth two stroke. I didn't get a chance to really lean it out plus this was the 3rd tank of gas that the engine had run so it may improve. Spin up time was pretty slow though. It was very happy with a low idle. I took off.... slowly. The tigermoth isn't a fast plane by any means but this combo was less powerful than my .91 glow fourstroke swinging a 14x6. It was acceptable though. The 10 mph winds meant I was often hovering if the throttle was 3/4 or less. Came in for a nice soft landing. I don't think this could pull it through a loop without a good dive.

So. Here is my questions.

What ratio fuel are you running? I ran the first two 24oz tanks on 32:1 and for the flight I tried 40:1. I had opened up the stock exhaust to 1/2 hole but did not drill through the internal baffle. Not sure if that is a big cause of the lack of power. Also I don't have a velocity stack. Not sure how that affects it. I have read about replacing the carb to get the extra power. Wackerengines has them for $20. Just not sure if the engine will gain a big performance difference. I am going to buy one of their mufflers because my plane after the flight was spotted with dark exhaust residue. I am guessing I must be still running rich because I though the point of going to gas was to have less cleanup too. The residue was harder to clean than glow. I have a couple of 15x6 props. Do you think these are a better match or should I continue trying to get the 16x8 to work? Oh, and here is a big one. I have a escort wagon. How do you keep the smell of gas from getting all over the car?