port matching exhaust gasket / muffler inlet / cylinder exhaust port on MS660

[lectrocrew]

I was modifying the inside of the muffler on my MS660 saw (shown on this page) and noticed the gasket is not as wide as the cylinder exhaust port or muffler inlet. The height is fine. I trimmed what material I could without cutting into the actual seal surface of the gasket and it now matches the muffler inlet opening pretty well but there is ~.050" more width needed on each side of the gasket and muffler inlet in order to match the cylinder exhaust port.
Has anyone got any info on the best way to match the gasket to the cylinder port without cutting into the gaskets raised seal surface? Is there a wider gasket or a flat gasket available? Or am I better off making my own?

The following photo's show how much I trimmed the last gasket to match the muffler inlet compared to a new gasket from Stihl (part # 1125 149 0601)?

picture 1 (new gasket on bottom)

picture 2 new gasket on bottom)

picture 3

picture 4

picture 5

picture 6 (new gasket on bottom)

 

[Mad Professor]

The last one I did was an 038 and after cleaning up the exhaust port I ground the muffler and gasket with a dremel.

If you are worried about sealing a light coat with a sealer designed for automotive headers will work. I'm pretty sure that raised surface just gets flattened out when you bolt on the muffler anyway.

 

[lectrocrew]

Okay, I got the cage cut out last night at work with no problem. Those spot welds holding the bracket to the muffler housing came apart real easy without deforming the housing after the initial cuts were made with the plasma cutter separating the cage into 3 sections. I cleaned it up with a buffing wheel on my die grinder then fabricated a 1/8" stainless plate that will span the entire rear wall of the housing and serve well as a support so the vibes don't fatigue the thin wall housing material left after removing the cage. I milled the port in the stainless plate to match the cylinder port and ground the muffler to match both with the die grinder. When I resume this project, I'll spot the stainless plate to the muffler housing with the TIG, cut a new gasket from high heat 1/16" header gasket stock, and install the assembly with 3/16" longer stainless bolts with antisieze lub. All that will be left is for my dual port cover (#1122 140 0800) to arrive at my Stihl dealer sometime this week (it was supposed to have been here Monday but was not.
I can't take any photo's of the project since no cameras are allowed inside the plant where I work, but I'll snap a few shots of the finished product before I install it.