Onan 4K spark arrestor plug won't loosen for removal

maillemaker wrote:
Over on the SmokStak forum they said they are hard to get out, and if you try you should use vice grips on the mounting boss, otherwise you can rip it right out of the muffler sheet metal.

But the guy said once he got it out, hardly anything came out of the muffler anyway so it probably wasn't worth the effort.

Kroil is another good penetrating oil. I tried it on mine and gave up trying to get it out.

Steve

I had the same problem getting mine off. Soaked it in Kroil oil for several days and it would not budge. The screw came out but the spark arrester was rusted to the tail pipe. Finally I took a propane torch and got it hot then tapped the edge of the arrester with a hammer and screw driver around the circumference and it came off. I had about 350 Hrs on the genset and it was 12 years old at the time. There was not much carbon buildup on the inside screen. I imagine if the genset is running rich, carbon can build up quicker.

bounder39zman wrote:
...as a generator tech who has serviced hundreds of these generators, I don't think I've ever actually gotten any appreciable amount of carbon out of muffler when removing plug...

That experience just made my prospective plan permanent: Leave It Alone!

Thanks!

as OP stated, WD40 not best penetrant...Kroil is best ever, PB Blaster good also. The plug in muffler is a tapered pipe thread, and if it is rusty, probably will not get anything to penetrate and loosen. I have used an impact gun with a tight fitting socket, and "gently " vibrate on plug until it loosens a bit, then spray with penetrate and finish removing. However, as a generator tech who has serviced hundreds of these generators, I dont think I've ever actually gotten any appreciable amount of carbon out of muffler when removing plug.

Thanks to all, I'm going to let it be. I don't want to damage the muffler.

If you want to peruse it, I think the heat wrench is the best try.

Don't know what you have for clearances but i have used the correct size ( smaller for restricted spaces) torch and went to the cherry red point and then let it cool down and give it a try. :h

Over on the SmokStak forum they said they are hard to get out, and if you try you should use vice grips on the mounting boss, otherwise you can rip it right out of the muffler sheet metal.

But the guy said once he got it out, hardly anything came out of the muffler anyway so it probably wasn't worth the effort.

Kroil is another good penetrating oil. I tried it on mine and gave up trying to get it out.

Steve

I'm not going to worry about it and I'm going to leave it be. Not worth risking damaging the muffler.

gbopp wrote:
WD-40 is not penetrating oil.

Buy something like PB Blaster or make your own with Acetone and Automatic Transmission Fluid.

First off, I completely agree with gbopp. WD-40 is NOT a penetrating oil. You are MUCH better off with PB Blaster.

When I finally traded my Class C after 10 years, I still had never been able to get that off. I didn't worry about it.

gbopp wrote:
WD-40 is not penetrating oil.

Buy something like PB Blaster or make your own with Acetone and Automatic Transmission Fluid.

Only issue is I am spraying on the bottom of the bolt as it screws in from the bottom like an oil pan plug. Tried heat, WD40, tapping with a hammer and nothing except the square top of the plug looks like it may break off and then I'm really in trouble. Some of the thread are showing and I may be able to get vise grips on the threads but it will really tear it up. I removed the tail pipe next to it hoping I could spray some WD40 or rust penetrating fluid, but it go straight up into the muffler. So no way to put fluid on the threads inside the muffler. Not sure how much penetrating it will do from thee bottom. May just leave it alone and hope nothing ever happens because I never cleaned the spark arrestor. I'm sure may have never done it.

WD-40 is not penetrating oil.

Buy something like PB Blaster or make your own with Acetone and Automatic Transmission Fluid.