Inspect the needle, and ensure that it is inserted onto the needle bar correctly. There are two things to look for.
1) That the eye of the needle is not facing to the left at all, you can have it facing straight on and slightly right but never left.
2) You need to ensure that the correct side of the needle is facing the front of the machine. On one side of the needle there is a long groove that starts from the eye of the needle and goes all the way along the shaft of the needle up to the part where it starts to widen out. On the other side just above the eye of the needle is the scarf of the needle, a slight indentation cut out of the shaft of the needle.
The groove that runs from the eye up to the wide part of the needle must fact towards the front of the machine, this will ensure that the scarf is facing the rear.
If your needle is inserted correctly. Look at the back of the design and see what the ratio of upper thread and bobbin thread is on the back of any design you've just sewed out. If you see too much of either and no balance then your thread breaks could be caused by tensions issues.
If the tensions look ok on the back of the design, and by this I mean you have a good balance of bobbin and upper thread on the back of the design. The bobbin should be centred in between the coloured or upper thread. Then you'll need to check your hook timing. I just written a post on this yesterday I will copy it here for you to follow.
You may want to check your hook timing, to do so follow these steps and let me know what you find.
1) Set your machine to needle number 3, by pressing the number 3 on the control panel.
2) Remove the needle plate.
3) Power off the machine.
4) Rotate the main shaft wheel in the back of the machine two whole rotations then set it to 200 degrees.
5) Your needle should be all the way down now, look behind the needle and locate the hook point located somewhere behind the needle on the rotary hook. The hook point will be the tip of what looks to be an open end of a pair of scissors. The tip should line up right behind the needle, and the gap between the needle and the hook point should be about the distance of a slender business card, or 1/2mm. Push needle 3 backwards towards the hook point and see if the hook point is resting up against the back side of that needle, if it is then the rotary hook is breaking the needles, and you will have to adjust the hook timing.
That rotary hook spins and the hook point picks up the upper thread and joins it with the bobbin thread, If the hook point is too close or resting against the back of the needle, then the rotary hook point is snapping the needle as it makes contact. There needs to be a gap as I mentioned of about a half a millimetre.
If the rotary hook point is not aligned directly behind the needle, than slowly turn the wheel in the back of the machine until it does line up behind the needle, and let me know what degree the wheel is set to when the hook point does line up directly behind the needle. Hook timing is optimum at 200 degrees, but it can be set anywhere from 198 to 202 degrees, depending on how long the eye of the needle is. If your hook point is lined up behind the needle less than 198 or more than 202 then you will have to set hook timing.
Here is a link where you can watch how hook timing is to be set. Now on the video you will see that they remove the black support bracket. If you need to adjust hook timing, you do not need to remove this support bracket. The only time you need to remove this bracket is if you need to replace the rotary hook, or if you have burrs or nicks along the leading edge of the rotary hook. It is entirely possible that your rotary hook has a burr on it, which when the thread glides over the burr or nick, it would cut it, causing it to fray up the length.
So it might be a good idea to run your thumb nail along the outer rim of the rotary hook, Again you do not have to remove the rotary hook to do this, just turn your main shaft to 140 degrees and run your thumb nail along the rim of the rotary hook, Start at the 9:00 position and round your thumb nail down and around to the 3:00 position and see if you feel any nicks or burrs. If you do get an emery board and instead of removing your rotary hook to buff out the nicks, you can do it while the rotary hook is mounted to your machine. After you've buffed out the burrs then polish it with a piece of crocus cloth.