Janome sergers need regular maintenance, just like a sewing machine. Sergers get especially dirty, due to the lint created by the fabric cutter. If you look in a Janome serger instruction manual, you’ll probably find a diagram that shows how to oil it, and at least once a year you will want to bring the serger in to have it serviced.
I’ve seen a handful of sergers come in that were totally seized due to lack of oiling the upper knife linkage, so I thought I’d post a picture and show where the oil holes are.
Click on the picture to see a larger version, so that you can see the oil holes. You’ll want to use a good quality sewing machine oil, and place a drop in each of the holes. If you use your serger a lot, I’d recommend applying the oil at least once a month.
If you’re not comfortable doing your own oiling, you can bring it to me, and I will do it for you. I would rather see you happy with a serger that works than a serger that is frozen.