How to clean the spark arrestor RV QG 4000

It should be a plug on the muffler

Maybe two plugs, let it run for about 5 min. with the plugs out. Some things approved for forestry say to plug the end of the muffler for a second or two with a gloved hand a few times but that was a long time ago. Maybe OSHA doesn't Nike that any more.

if you crawl under your generator and look up where the tailpipe comes out of muffler housing, you should see a pipe plug in muffler canister. If you remove this plug and run genset for 5-10 minutes, you should clean the spark arrestor which is built into the muffler. However,
in my opinion, (30 yrs Onan tech) about every 500 hrs is more reasonable service recommendation. In fact, don't know that I've
ever seen one of these plug up to point where exhaust is restricted.
again, just my opinion.