The Skyline series does not have tension disks, but the HD9 does so I think that's the confusion.
There is a tiny wick in the center where bobbin case sits. Touch it with your pinky tip and see if any oil shows on your finger. If yes, it's fine. If no, you can carefully put a drop of oil there. Being a bit dry though, shouldn't have any real effect on the sewing tension.
Is this is a new problem, or a new to you machine?
Are you using the same weight top thread as the Janome bobbin thread?
Have you tried a different spool of thread?
Have you tried a different bobbin thread?
Are you making sure the top thread is snapping under the guide plate (see step 2, p 16 of manual)?
If the guide cover is removable, lift to check for any dust bunnies. If not removable, use a piece of dental floss as thread to guide through the slot for cleaning.
Have you tried a different size needle?
Have you tested other fabrics, eg plain weave cotton and batik?
Last but not least, have you tried a heavier foot pressure?
There are so many things on the machine that can affect thread tension, but different fabrics will also.
Hopefully you'll find an answer. If not, it might need tech adjustment. It's not unknown for them to be too tight coming from the factory.
Jan in MD