Wanted to revive this thread as I am back to tinkering with this engine. I have a cmp 90-120 size cessna on its way and am hoping to use my 25cc wacker for the plane. Since my last dealings I have gotten a nice aluminum pitts muffler and a 15mm walbro carb. I have gutted the intake to match the carb with a smooth runner. My engine is the version that has 4 bolts in the rear housing and 4 transfer ports and single ring. I have also dremeled in the intake and exhaust ports slightly to open them up on the sides another 1-2mm (which produced an additional 300rpm gain on the 16x8). I checked my compression and I get 120psi of compression which seems nice and high compared to others. Running 40:1 mix with 93 octane I get the following:

16x8 MA 7300 rpm
17x6 APC 7800 rpm
17x6 APC 7650 rpm with one pipe plugged on the pitts (which cuts down noise by 50% !!)

I have seen others stating that they get 8k on the 16x8 MA. Not sure how, my engine probably has about a gallon through it and it can't make it there. However, the 17x6 readings look promising and much better than my previous tach of 6400 on the 16x8 with the stock carb and exhaust. What do you guys think? Will she fly the cessna in the constant 10mph winds here in illinois? On that tigermoth it was a dissapoinment as it put out about the same as the 91 fourstoke powerwise but it has pepped up quite a bit and I expect the cessna to come out around 13-14 lbs. Not looking for 3d just the occasional loop and could live with it if I have to dive briefly. Any other ideas to bring up power?