I don't think running rich will make you seize. However, running low on oil might!
The oil injection pump is set from the factory to lubricate a stock 50 cc cylinder. It may not have the adjustment or the output to lubricate a 70 cc motor.
You may want to consider premixing some oil in your gas to supplement your oil injection pump to lubricate your big bore cylinder. I had a friend that seized a Malossi kit from insufficient oil. I had a friend who seized his stock motor rebuild after rebuild because the oil pump failed too. Oil is life to a two-stroke.
Too rich might lower your top speed though, so that's not desirable either.