Experience tech have a phrase for those engines. “It take courage to buy a Courage engine”. Sounds like you’ve decided to repair it, which those same techs have done when the customer wants to go that route. I’ve done so myself, but have a warning to those customer’s to try to alleviate the problem in the future. I tell them at the beginning of each season have someone, if you can’t do it yourself, to remove the shroud and check the crankcase bolts making sure they have not come loose. If you don’t have one this manual may help you out.
https://www.mymowerparts.com/pdf/Ko...urage-SV470-SV480-SV530-SV540-SV590-SV600.pdf