I know they are expensive and few people work on them. I’m lucky to have a Cummins Distributor in Wisconsin which I am able to call and get parts. Because most people won’t touch them I’ve gotten units from 100 miles away bring them in for service. About 10 years ago guy calls and offers me a free weekend at his resort in northern Wisconsin plus my labor rate if I would come and get the generator on his RV going. Boss said go for it, the next week packed up the wife on Thursday, drove 125 miles, and got a two bedroom cabin on the lake. Next day did a full tuneup on the unit and relaxed for two days. Guy covered our meals and drinks, paid for mileage and three and half hours labor, and the next five springs drove it to us for a tuneup. Everyone, including the wife, was happy.