Oh dear, always that one who did some repairs in the past, and not passing on the info. Having similar frame issues with my SST GP build. (being built on the Kickback Garage channel) Oh well, Lambrettas, another day, another problem. Best of luck Iggy, the RT 225, such a lovely engine.
Yep I had a brand new 200 Indian casing from rayspeed 20 years ago and I just couldn’t get it to run right turned out small crack on the barrel stud holes bought another case. Fixed the problem immediately,,,,