I bought the same exact levers from the same company. No problem with the brake lever but I had the exact issue you are having with the clutch lever. I sent them an email explaining the problem. They replied and asked me to take some close-up pictures of the inside of my original clutch lever (where the round brass insert is) and email them. I did, and then they mailed me a new brass insert with a deeper hole. I removed the old one, replaced it with the new one, and now I have perfectly working levers.
Yes, a pain in the a$$, but I think it was better than having to hassle with international shipping and wondering if you'll ever receive a refund. And also the post took a long time to get here.
Personally, I think the quality of the lever is great for the price, and I have buddies that bought them for their Ninjas, GSXRs, etc and they have not had any problems...but the company definitely has not fixed the issue for the C-14s.
Good Luck.