Inside HI-COMPESSION MUFFLER.
Do the extra holes mean more flow?
I'm not sure I understand back pressure?

[Linked Image]

To finish this mower, I just have to sort out the self propelled arrangement with the idler wheel and how the cable makes it tension the drive belt.
If someone could put up an image, that would be much appreciated.
Thanks from Mark

Happy is he who penetrates the mystery of things.