Lou,

I tried that as well on 2 different ones and yes it does give you the pressure but it also chokes the engine. Once I started using 1/8th inch line and reopened the tube then it ran like it should. If you have seen the video of whaturi flying his Cap on an OS160, that is one of the engines I sold him, using a brisson muffler with both tubes open and 1/8th inch line and it's a real powerhouse.

The OS 160 does not really need pressure to run on this plane. The little bit you do get from the Brisson and the is more than enough on the 1/8th inch line

Check over in the OS support forums. They tell you not to crimp the tube and run the larger line....