Add some oil to get about 32:1 but don't use outboard oil. It's different than air cooled oil. Something with the ash and ashless and etc. Always best to run heavier on oil than lean. Haven't fouled a plug yet at 32:1 so...
Even at 32:1 you have 1/2 the amount of oil. 50:1 is way to lean on oil for these IMO. It might work but you should know if it doesn't by the bottom of the first tank full.
Best to give it a rip and get it all running BEFORE paint. You may need to remove the cover a couple times and noth'n suck worse than scratching up new paint. $0.02