Kohler command 12.5

Working on a miller welder/generator with a Kohler. Found several issues but the one I’m looking to address currently is on the cylinder head. Where the muffler attaches to the head around the carb side bolt threads it’s all “washed out” by exhaust gases I’m guessing.
Could I repair this with some steel putty?
Is this a sign of a blown head gasket?
Is this a sign of issues with the exhaust valve?
The muffler mounting bolts were really loose

Having issues posting pictures but the issue is not with the muffler, it’s with the cylinder head where the muffler mounts to the head. It’s missing metal around one of the bolt holes. Kohler Ch12.5S I believe is the model number. And no studs, bolts go through muffler and into the head

Yea I’m not to sure bout the JB weld idea either but I did buy something they make called extreme heat. It’s like a hardening epoxy paste product that is supposed to be good for 1000 degrees and lists exhaust’s as something it’s used for. May try it for chits and giggles. I can’t weld aluminum and would have to take it to someone for that repair. Mainly trying to get this thing running to verify power output from weld leads and the 110 receptacles before diving any deeper or sinking much money into it. It’s 1995 Miller Bluestar 180k with about 700 hours on the clock

Ok so to confirm valves are not the issue I did a leak down test today. Only 10 percent leak down so good there. Have good compression, valves are indeed working, have spark, have a working carb. Still runs and dies and backfires. So I have not pulled flywheel to check key but don’t think it’s sheared when rotating flywheel by hand the magnet is just clearing the ignition coil on TDC so that seems to check out in my book as in time.
Think I’m going to slap a new coil in it and see if that’s the issue. I put a new plug in it already even though plug was fine that was in it.

Appreciate any thoughts or expertise fellas

I have an in-line spark tester, never used it until now but when hooked up it’s flashes consistently but the light is orange. Shouldnt it look blue if spark is strong and orangish if weak? This is what led me to further suspect the coil

Chased kill wire from ignition coil back to switch on side of welder and where it plugged into the switch there was another wire there. Chased that wire and found it provided power to the oil pressure switch. Unplugged it from that switch to retest and wouldn’t you know it bam engine fires up and running like a top. Bad oil pressure sensor!!!

Tested all receptacle’s and they were provided 120 volts. Hooked up a light and a grinder and they ran fine. Decided to hook my welding leads up to it and burnt a rod of 6011 without issue. We are back in business baby. Need to button everything back up and give her a cleaning. She has also earned an oil change!

Minor issues still need to address. Believe she is running maybe a 100 RPM to slow. She was showing 58.5hz and tried to make adjustment on carb with no increase. Maybe need to look at the governor setup and see what I can do there. Says on the cover should do 60hz at 3750 rpm. I would think from other generators I’ve checked that it should be around 61.5hz

So there was indeed an engine speed bracket with two set screws on it that the governor spring attached too. Loosed them up slid the bracket over about a 1/4” and that brought things up nicely. Left it set at 61.8-62 hz which is roughly 3710-3720 rpm. Slightly below rated max for this machine. Gonna start cleaning up some old grime on it, wrap my wiring harness back up and just generally button things back up. But it sure appears I have a viable machine here again