I will offer my humble opinion if I may... I have 6 Evo's... 2 .46, 2 .61, and 2 100's. I had no problems with the .46's, they are more powerful than my O.S. .46 FX, which runs well too. I expected the same out of the .61 & 100, but I had the same problems you are having, i.e. inconsistant carb settings, lean outs, floods, dead sticks... it seemed like every different attitude my plane was in would bring on a different symtom. I was so sick of the 100... I tried EVERYTHING TO GET IT TO RUN RIGHT. I worked on that thing for months it seems. I even bought a new one and tried it, & it had the same problems. Then I got a wild idea. I would try adding a little restriction to the muffler. It just might be crazy enough to work!

So now I offer you a simple solution that has me jumping for joy again... try increasing the muffler back pressure slightly. While at full throttle, I did this by CAREFULLY (remember the prop!) squeezing the exhaust pipe with pliers just until the engine starts to decrease rpm, then I opened the crimp back up with a flat blade screwdriver JUST until it had full song back & then reset the high and low. IT WORKED LIKE A CHARM!!! I couldn't believe the difference! Now the .61's and the 100's are dead reliable, and powerful! Especially the 100, (also mounted inverted) which I thought was doomed to the sledgehammer for sure. you could also try putting a silicone muffler extention on the exhast and crimping it down a little with a zip tie if you are worried about taking pliers to your muffler. Easilt reversible and cheap. Don't give up on this engine as I almost did. While the root cause of this problem may not be muffler design, the CONSISTANT fuel draw problem with these larger EVO's can be cured with no loss of power with this method if done properly. Try it and let us know how it worked- I sure am smiling again.

P.s. This isn't Evoution public relations, just me showing you how I got the most out of my substantial investment. Still, I don't really know how they missed this in the "factory" break in and adjustments!