It will richen up some, but probably not near enough to really tell. The amount of fuel/oil change is very insignificant in regards to the air/fuel ratio. If your good at 50:1, then you should be fine at 80:1.
If there is a problem, it should begin to sputter or something indicating a rich condition, and this really won't hurt anything, so I'd just switch the ratio like you want to do and then go out and run it. If it's too rich, then you'll know and you can rejet accordingly, if it runs fine, then go out and have fun.
Later.