Hi Dave, I looked at your Weedeater again. My FL-25 and the two 21cc engines I have, don't have your bigger type muffler. My Weedeaters have the smaller silver ones. I am in the process of making an aluminum muffler for the FL-25. This is a bit of a challenge since these mufflers are held on with springs and not bolts. I see why you reversed the cylinder. I converted the two 21cc Weedeaters first. With the first runnings, I got 6000 RPMs with a 16-8 MA prop. They run pretty smooth so I started modifying. I cleaned up the ports, I opened the intake a lot, I drilled the carb spacer to 1/2", and changed the card to Zama carbs from 32cc MACs. Now I get 7000 RPMs with the same prop. I did one other thing and I am not 100% sure if it was necessary yet but I like the way they run, still smooth and a bit easier to start. I machined .030" from the bottom of the cylinders. 7000 RPMs with a 16-8 prop from 21cc seems like it will be usuable. The FL-25 has more compression to begin with and the ports are also bigger to begin with so I am interested to run it after the conversion is finished. I am going to change its carb also as the main change. I hope it runs as smooth as the 21cc versions. One other point is that these engines are not terribly loud without a muffler so that is why I am making a muffler to try on the 25. (Working on these engines has become another Hobby in itself)