Too much 2-cycle oil in the gas will foul the spark-plug, and way too much will make smoke in the exhaust, and foul the spark-plug.
After the spark plug fouls it will be hard to start, and it may not start at all, until you put a new spark-plug in it.
Too much oil in the gas will cost you money for spark-plug, and make more air pollution in the exhaust. And after too many repeated replacements of the spark-plug you may strip the threads for the spark-plug.
I once worked for someone who was (to say the least, not very good at math). And this person had seniority, and to top it off had an attitude that no one with less seniority could tell him anything. He also had a bad temper, and at a later date was found to be using cocane.
Anywho, one day he is making up a new batch of gas for the chain saw. His boss had told him to be sure to add the correct amount of oil to the gas. So he puts one gallon of gas in a red plastic gas jug made for one gallon and dumps a 8 oz bottle of 2 cycle oil that said 32:1 on the label. I saw him do that , and in my head did the math.
1 gallon = 128 oz.
128 / 32 = 4
So he should of used 4 oz. , but he had used 8. So the mix is now 16:1 but knowing this person, I did not say anything.
I suspect that he may have notice that I noticed and thought something was wrong, but I am not sure.
He then picked up another 8 oz. bottle of the 32:1 2 cycle oil and dumped that into the gallon.
Now the mix is 8:1 and I still did not say anything.
We used that mix, and boy the smoke that chain saw made was enough to fill an entire valley.
About a week later he comes into work one day all mad and starts talking about how his kids teacher tells him his kid is no good at math. I still said nothing, but had a hidden laugh about it thinking about the saying about how the seed does not fall far from the tree.