i got my 79 moby last august and besides problems resulting from me not yet knowing how to maintain it (you have to grease the transmission and the pedal arm nipples or you'll have troubles) it's been great. it starts right away every time and has average acceleration and a bit above average speed i'd say (i get like 37 mph on a straightaway). luckily no work has been required on its inside though because it does look like a real bitch to work on. so i have to keep crossing my fingers there.
as for oil mix right now i'm running 6-8oz per gallon which is up from the regular 4oz i used to put in. but sometimes after it gets tired from hills or long rides it seems to slow down sometimes almost to a standstill so that's getting me worried. hmm i guess that could be translated as a problem. doh.
wish me luck