I get a check the hook system message but I don't know how to do that. I have a 730 machine. Also the needle keeps breaking. What should I do?

check the age of the cotton
cotton is not a single thread but a series of fine threads bonded with a glue
old cotton glue breaks down and the thread separates easilty
next check that the needle is installed correctly with the grove ( thread groove away from the bobbin hook
check the needle and hook timing because if it is off a fraction , the hook will pierce the the thread causing it to break
next check that the eye is the correct size for the thread in use
a needle eye too small for the thread thickness will jam the thread ans not let slide through the eye properly

use a bigger eye in the needle and loosen of the needle thread tension a bit
needles are all the same length but come with various size eyes to accommodate thicker or thinner threads
use scrap material until you get a good combination

possibly the top thread is being restricted in movement
check that the thread is between the tension plates and not behind it or knotted up in the way it is threaded
pull on the needle thread and it should move with a steady pull not very hard
if it is not moving fairly easily the check how you have the thread installed
also old thread will break easily as the bonding used to keep the strands together breaks down and is difficult for the thread to slide though the needle
another point is the needle to hook timing and the clearance there as well .
if there is a problem there , the hook will split the thread from the needle and break it
if you still have problems , take it to a sewing machine service center ( any one ) and they will advise of the problem and show you how to fix it

since the bobbin case is moving, the machine needs to be checked again, and this time the hook and hook race needs to be looked at, could also have a timing problem with the needles breaking.

try changing the needle
try turning the bobbin the opposite direction in the case
make sure the top thread has not come off the thread take up lever
clean under the needle plate and in the bobbin area for lint
if these suggestion don't help then the machine needs to be checked

Well, you've not checked "Everything" but you have checked the common things.

Do you have any idea of where it is actually breaking? Re-thread your machine and see if you can determine exactly where the break occurs.

Sometimes a damaged needle throat plate will break threads... as will a burr on the hook in the bobbin area. Also if there is a burr or rough spot on the thread spool it will sometimes catch and cause breakage.

Good luck

The 730 rotary hook is a bit sensitive to adjustment and cleaning. Make sure that the hook is clean and if you haven't oiled it for a while, give it a drop of oil (do you know where to put it ... many dont !) Check your needle is OK and, again, if used for a while, just put a new one in anyway. Load-up with different colours of the same type of thread top and bottom and sew-off a sequence of zig-zag, starting with the default and increasing the width and reducing the length until you get to a maximum width satin-stitch (dont increase the bobbin or top tension as you do it). Once you've done that, let me know what it looks like. The colours should be equal top and bottom, but maybe just a bit of top coming through to the underside on max width satin stitch. You'd also be advised to sew-off using pattern number 437 and the figure '9' - this will check the balance of the machine. If the '9' is not perfect, or the top section of the pattern 437 is not dead-central on the top of the triangular part of the pattern, the balance may need adjustment. Let me know how you get on.

Don't be dictated to by computerized machine, as long as you keep the raceway clean and a few drops of oil and it sews okay then you will be okay

Sounds to me that your machine is out of time. I recommend you take it to your local repair center.

I don't know for sure, but I have found that a dull needle will cause the thread to break. We have fixed many machines just by changing the needle. Try it, it may fix the problem.