Do you think you can lose a client's interest by over explaining your product or services?

Beyond a doubt, you put yourself at risk of losing a client's interest when providing "Too much information" (TMI)).  The operative word is "YOUR".  The only one in love with your product or service is you.  The vital focus should be on listening to the customer's need.  Your product or service is the solution to the client's need or problem.  Ideally, you should identify the client's problem first so that you present your offering as a solution to the problem or need.

I definitely believe in the KISS methodology, keep it simple stupid

Most definitely. This is something I have known and done intuitively always. It was based more on what would I not like. If I wouldn't like it, why would anyone else?
So yes, KISS, TMI and all the acronyms, but above all learn to listen not only to what is asked but "listen" to body language, faces, eyes, trying to move away and you will know pretty quick.
One way speaks to desperation, the other denotes consideration and understanding.
It amazes me how often someone will ask me something and then answer with what they want to talk about not what I have asked for.

YES!

To be effective at selling it is more important to ask questions and be an active listener. Find out their pains and buying motivations and hit those nails on the head full force. If they are interested in every detail they will ask for every detail. The more information you give to them, the more opportunities to say they have to "think about it" or "check with their ______." Easy acronym for selling, KISS. Keep It Simple Stupid. Keep it simple and focused, hit the objectives and shut up. 

It is more important to use active listening to find out what they want. If the features and benefits are few but you have many, hone in on only the ones they will get emotionally attached to. Telling is not selling. If you're telling, you're not selling and your numbers will show for it. 

 Transparency is always good you want repeat clients, You get that by gaining there trust for a long business relationship. Something went your explain your product the question they were assuming the answer to is clarified.

The conversation should be about the client, their challenges and issues first. If your products or services are a solution to make their life better, then weave them into the conversation. Don't just spew about everything you offer. It has to be about what's in it for them.

I was taught many years ago that "clear and concise" is the byline.  It's similar to KISS, but the importance is communication.  

If you overexplain after your clients understand, you tend to bore them and eat their time.  If you try too hard to make it "simple stupid", you can insult their intelligence.

Think through your message to make sure you cover the subject to the extent the clients want and need.  Always keep an eye on their face.  If their eyes start to flicker or stray, you are talking too much.  If they "glaze over", you are over their head.  If they seem to want to say something, let them.

By all means, keep them in the conversation.  They will let you know when they "get it" by their questions or comments.  

Communication is a two way street.  No one like a lecture.  And if you listen and pay attention, you will discover the clients' concerns and agreement.  

Then everyone gets value for the time spent.

Sure. That's why it used to be taught to listen for the client to say "YES" without actually saying "YES"...then just shut up and write up the sale.

It also goes along with what I do: I never convince anyone to use my product, me, etc. If they aren't already interested, I'm not here to convince them. There are plenty of people that are interested, that I'm passing up, every minute that I'm trying to convince someone else.

100% yes you can lose them by over or under explaining the product or service. Stop selling or talking about what it does. Explain what they will get out of it. Use a case based on their business needs to help any level you are talking to better understand the WIIFM (what's in it for me) and by all means follow the KISS method unless your product or service is detailed, but even them tell how it will help with what THEY do.

Absolutely. Have you ever heard the old saying, “It took you 5 minutes to sell them. Then you spent another 20 minutes talking them right  out of it!” It’s true. Give them the information they need to make an informed decision of course, but when you get the buying signal, shut up and start writing the order. That also leaves you plenty to come back to discuss in the future and that is where you build the true “client”relationship.