The most important moment for a new engine is first start-up. I use 'Graphogen' engine assembly paste, on all the bushes and contact surfaces, which prevents metal-to-metal contact before the oil starts circulating properly. I make sure the pump is primed and I kick the engine over, without the spark plugs in, until oil flows out of the PRV. I refit the PRV ball and spring and kick the engine over again with the return pipe off the crankcase until oil flows out of the return union on the crankcase. On starting the bike I check the oil return at the tank and, as soon as it starts to flow, I put my finger over the return hole to encourage oil up to the rockers. Those of us of a certain age will remember 'Red-eX', which was an upper cylinder lubricant, which we treated our bikes and cars to occasionally when we visited the petrol station. TBH, I'm not convinced it made any difference. It didn't do any harm either. Putting oil in the fuel is only going to affect the bores and valves, and only minimally compared to the splash from the crank and the rocker feed splash to the valve guides. Critical parts of the engine, like the timing side bush, big end shells, camshaft bushes, need all the help they can get at start-up, and oil in the petrol isn't going to help those.
