RE: spark plug falling out of zdz 80???????????
Yeah, that's what I thought had happened after I reread your message. The first time I used my engine, that happened and it was because it was not tight enough. Got the bigger monkey out and it's never happened again. Just to be on the safe side, after a day's flight then check again. If it keeps loosening up, then there must be some other problem- maybe with threading? I've never needed an additional washer.