I had to enlarge the inner diameter from 4 3/8' to 5 1/4' to match the ID of the burner housing, but that took all of 5 minutes. Monitor wants ~$20 for the part, but I found a similar 6 5/8' diameter gasket at a heating supplier for $3.49. The gasket at the bottom of the burner will need to be replaced. Lay the housing on it's side when removing the burner pot and it's four screws. Otherwise, loose debris will fall into the end of the housing where it can be difficult to remove (it gets caught in baffles in the housing). Avoid inverting the burner housing until after you've removed the burner pot. I installed a 1/4' socket on the end, then inserted a Phillips screwdriver bit. I used 1/4' drive screwdriver handle with a pair of 10', extensions on it to get the necessary length. It's necessary to get to the left rear screw that holds the burner housing to the base (and it's handy for the right-rear screw). The one special tool you'll need is a #2 Phillips screwdriver that's ~24' long. Keep the screws with the parts they attach. If you're not sure how the heater is assembled, take digital pictures of the process so you can easily retrace your steps. I stumbled upon a copy that was posted online, but couldn't find it again. Directions for the job are included in the repair manual (~$30).

Here are a few tips for anyone considering this job. Now, I can rebuild the old burner pot at my convenience and have it ready when I need it in 3 years or so (I vow to do maintenance as necessary, this time). The reason I spent the extra money this time was that it was the middle of the heating season and I didn't have the time to clean the old burner pot and wait for the cement for the burner cloth to dry (~24 hours). I plan to rebuild the original burner pot by cleaning it and installing new burner cloth, so I'll only have to buy a new burner ring next time ($75), saving me $125. Although it took me ~2 hours, the next time it will take considerably less, as I know exactly what's involved. It was a much easier job than I anticipated. I ended up rebuilding it with a complete new burner pot and flame ring ($200 for the parts). In online/email conversations with Monitor techs, I was told that I needed to replace the burner ring and burner cloth. I knew it wasn't running efficiently and $3/gal kerosene provided the incentive I needed to service it. The unit was WAY overdue for basic burner service and I had been putting up with these problems for a couple of seasons. The flame was yellow and flashed frequently. The flame sensor kept shorting on the burner ring, shutting down the heater. My Monitor 422 was 6 or 7 years old (with no maintenance) and had the following problems:

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