The remainder of my short N-V career involved the AJS Stormer street/trail bike. We were still trying to figure out why the Starmaker engine, which was virtually indestructible in continuous high power use (moto-cross racing), was destroying itself with piston ring/cylinder "welding" in street use. I rode the prototype from home to work daily, across Wolverhampton on city streets and the first liner was destroyed in about 500 miles. There were circumferential ridges around about 40% of the liner, centered on the exhaust port and about every 0.2 inches all the way up to nearly the top.
Using Castrol "R" in a street bike was our only viable early fix, but it couldn't have survived as a production set-up. I had to shake the bike for about 5 minutes before leaving for work to make sure the oil and gas had re-blended after an overnight stop. Everyone was still scratching their heads when I quit N-V and left for Boeing.