Should I have undergraduate class papers on ResearchGate? I just finished undergraduate and I am now in my first year of grad school and I am working on some real research projects now. I have one paper that I am already submitting to a peer-reviewed journal. 

I uploaded a few papers written for undergraduate capstone projects and final reports to my RG. They are never going to be published but I thought they were interesting reads anyways, they were all typical secondary student research papers.

If I went back and wrote them again, I would probably change a few things here and there, there aren't any glaring inaccuracies but none of the papers are journal quality.
I noted the fact that they were for classes in the descriptions.

I thought that was a good idea until one of them started to get more than 100 reads, now I am second guessing the decision.

Is it acceptable to have undergraduate class papers on ResearchGate? 
Could it harm my career if the papers are of undergraduate quality? Or is it a good thing to show your interest in different research topics at an early stage in academia?
From experience, both as a member of ResearchGate and as a postgraduate, I would say the main question is more about worth than about acceptability. 

Sounds like you did the right thing when you posted these papers the first time, with characterizing them as undergraduate works, therefore managing expectations.

You feel these papers may be of interest to others; fair enough. Statistics of opens and reads, and any message you get about them could be a good indication of how worthy they are to peers. If nobody gets to see them, you might as well keep them to yourself. 

Over 100 reads for an undergraduate paper sounds rather cool, and might give you an interesting clue about the popularity of your paper topic, and might encourage you to work further around the same topic for further research and papers.