Quick heads up, the 201 is a little unique compared to the other saws. You can’t just use a piece of rubber inner tube between the muffler and the exhaust port as there is a flange and you can’t use your standard block off plate - it requires a recess drilled into the stud holes. Just use a 7mm dia drill bit and go in 1/4” and then you won’t need to buy another block off plate. Just a little heads up. Normally a test is 10 mins. This required a bit of modification.
Edit:
I also wanted to confirm, that after drilling the holes larger, the block off plate still seals on larger saws so I tested my ms660 and it sealed perfectly.
Edit:
I also wanted to confirm, that after drilling the holes larger, the block off plate still seals on larger saws so I tested my ms660 and it sealed perfectly.