Spark Arrestor Cleaning

[04fxsts]

I have been trying to remove the plug on the bottom of the muffler of our 4000 Onan in the 2015 Ace without any luck so far. This is the first cleanout and the plug will not come out. I have used Kroil on it and even that has not managed to free it up. I have even tried to heat the muffler with a propane torch to loosen it but no go. Seems the metal is so thin and with a brass plug it takes the heat as soon as the heat hits the muffler. I will get it out even if I have to drill it out, helps that I used to be a machinist.
If I had a do-over I would have removed it before I ever run it and used some high-temp Neversieze on it. I also hate the square head on the plug, I will replace with a different type after it comes out.
Also any advise on some other way to remove the plug would be appreciated. Jim.

[westend]

I have sockets for a number of four sided plugs. Even so. parts that are heated to exhaust temperature and are of dissimilar metals become like "welded". One thing you might try is to heat the plug and surrounding exhaust and immediately quench with very cold water or ice. The dissimilar metals have different heat transfer rates and the introduction of cold after heating may break the bond.

[ksg5000]

I never could remove that freaking thing - on the bright side my Onan 4000 from 92 is still working fine - I doubt I am the lone ranger.

[bobsallyh]

04fxsts, for that stupid square plug, go to NAPA, and if it isn't on their tool board have them order you a 3/8" drive 7/16" EIGHT point socket. That will get on that wonderful Onan POS. I removed the arrestor and just put in a regular pipe plug with anti-seize compound.