ORIGINAL: tele1974
Got it ran on the pipe and wow. I ran a 18x6 prop and I got up to 8000 and it blew the pipe off.
You didn't specify which brand of 18x6 prop that you used on your MT-35 with the ES composite pipe but it sounds a little lacking when compared to the smaller MVVS 26cc which can turn an APC 18x6W at 8800 RPM on the standard muffled MVVS aluminum pipe. The 8800 RPM was achieved with a stock out-of-the-box 26cc with none of the hop-up mods that can be found on the Web.
Neither one of us may be giving enough details here to explain why such is the case but one factor may be that the MVVS was designed from the beginning to be a high performance model airplane engine while the MT-35 may be a very nice looking garden tool engine. I remember from the days of fast pattern flying that some engine manufacturers designed their engines with port timings that favored tuned pipes.
Is your pipe the correct size for a 35cc engine?