When sewing, mechanism sometimes binds. Bigger problem is when finished stitching, the hand wheel binds completely. Is there a mechanical problem or someplace to insert oil?

Not knowing the make of your machine makes it difficult to answer. However, if you have an older mechanical machine, the feed dogs could be seizing due to old, dry oil.

Wheel on right side that controls the needle up and down is very tight...

Take your presser foot off and the screws out of the plate. Lift the plate slightly and turn your stitch length regulator to the longest stitch that you use. Now set the plate back down on the feed dogs and see if it will sit evenly without binding. Loosen the feed dog screws and see if you can move the feed dogs enough to allow the plate to sit down. Now, retighten the feed dog screws and rotate the hand wheel towards you to see if they will move freely without binding on the plate. If all well, replace your plate screws and then rotate the hand wheel towards you again.

If this doesn't fix it, you may need to purchase a different # feed dog/plate. You might check to make sure that the items you purchased were meant for a Juki. Mostly they will fit different brands but sometimes it is easier to make sure that the combination of feed dog/plate is actually meant for your Juki.

The other thing you can do is to call a mechanic to readjust the machine to make these work (a more expensive option to be sure!). This has NOTHING to do with your timing. If your machine made good stitches before you change the feed dogs/plate. It should make good stitches after you change it. Timing is all to do with stitch formation and not stitch feeding. Good Luck!

The one thing on a sewing machine that needs the most repair work is the belt. The sewing machine belt is a piece of rubber that makes the wheel turn and the needle go up and down in a sewing motion. If the belt is in bad shape, the sewing machine will not work. Sometimes while sewing you may notice a burnt rubber smell. When you smell this, you know it is time to change the belt. Changing a sewing machine belt is fairly easy; just make sure you have the proper belt.

be sure to hold the top and bottom threads in back and away from machine as you start to sew. once you have sewn several stitches you can let go and continue sewing. sometimes this is all that is needed to avoid the "birds nest" on the bottom of the project.

Something is binding up inside. Clean and check under the presser foot and bobbin area. Really examine under there... look for threads wrapped around and in between moving parts. Also check in the slot for the take up lever... sometimes threads get balled up inside there can cause problems.

could also be a bent upper arm inside the machine (lets hope not) Get professional help if cleaning doesn't free it up.

Move the bobbin winder to LEFT. Sounds to me like you didn't re-set after winding a bobbin.
Hope this helps!
Jimmy

You might be in "Stopmatic" mode. Check if your pressure lifter bar is in the upper most position, if it is the machine is disengage and you are set to wind your bobbin. Lower it to the 3 o-clock position this will engage the machine and the needle will operate.

tighten hand wheel

The feed mechanism needs to be oiled. Take off the bottom cover and look for any place where two parts move against each other. Some binds can be very difficult to remove. Try spraying everything with a light weight oil (I like Tri-Flow) and let them soak over night. Then manually try to move the feed dogs with your hand. Hopefully it will break loose.
Good luck!

Take the needle plate off and turn the needle up and down by hand while watching to see if it is hitting anything. The hook timing could be off.