I have a white rotary 117-552. The manual said to use White Rotary flat shank needles only. Is there a replacement needle that I can use that will not harm the machine? Thank you for your input.

check with these sites about a manual & needles,,you'll need
to email them the name & serial number & ask them, they should
be able to help you
sewusa.com
sewvacdoctor.com
a1sewingmachines.com

Could be a couple of things:

Could be a bent needle? please change it for a sharp new one and make sure it goes in correctly, flat shank to the back.

Bobbin case dislodged or not in correctly ; I think these are vertical rotary hook machines with the bobbin inside a removeable bobbin case? Check that you have put the case in correctly, there is usually a long finger on the case that latches into a point on the rotary hook, holding the case in the correct position. Probably also a latch on the front of the bobbin case, which you use to fit it into place and remove it.

Lastly could be that the machine timing is out. Manually turn through a stitch sequence with no thread or bobbin, the needle needs to be at its lowest point down into the bobbin area when the rotary hook brings the thread around to catch at the back of the needle.

If you suspect it is the timing, you may want to get a technician to do this repair but certainly try the first two items first.

firstly check that the needle is in the right way, flat shank to the back. This is easy to get wrong and will prevent the rotary hook from catching the upper thread when the needle is at the lowest point in the stitch sequence.

Also check threading up of the top thread, particularly that the thread is through the take up lever.

There is good trouble shooting tips at http://www.sewusa.com/Sewing_Machine_Repair/Sewing%20Machine%20Troubleshooting.htm too.

However, if you are certain threading up is correct, and needle is correct then the timing between needle and rotary hook may be out. There is diagrams at this website too for this problem
http://www.sewusa.com/Sewing_Machine_Repair/Sewing%20Machine%20Hook%20Timing.htm however, I've always left timing repair to my sewing machine technician to deal with.

Check that the needle is in the right way, flat shank to the back.

Put in a new needle in case the current one is bent.

Failing the above, the timing between rotary hook and needle could be out and will need to be serviced

First check that the needle is in the right way, flat shank to the back, it is easy to get this wrong when changing a needle and it will prevent a stitch from forming as the rotary hook needs to catch the thread at the scarf (scooped out area) in the back of the needle to form a stitch.

Also, make sure needle is all the way up into the needle housing full.

However, if the above are not the cause, then it is possible that the timing is out on your machine and it will need a service to adjust this.

Check that the needle is in the right way, flat shank to the back. If it is around backwards, the shuttle hook won't be catching the thread at the back of the needle to form the stitch.

There could be several reasons for this fault:
Is the bobbin in the right way? Not sure if yours is vertical or horizontal hook desing. If you aren't sure on threading up then you could visit www.sewusa.com and search for your make there.
is the needle in backwards? you always fit them with the flat shank of the needle to the back of the machine.

And of course is the timing out? You need to manually turn the machine through a stitching sequence without thread and watch the rotary hook vs needle position. When the needle is at its lowest, the hook needs to swing behind it to catch the needle thread from the scarf (cut away) at the back of the needle.

sewusa also has some good images on setting timing - whether you tackle this repair yourself is up to you.

Have you changed the needle after the jam up? Clunking could be blunt or bent needle. Check by replacing with new needle, flat shank to the back.

Or it could be that the timing has been knocked out a little. So pull off the needle plate, pressure foot and take out the bobbin, then turn the flywheel manually towards you slowly and see if you can spot if the needle is striking the rotary hook?

If you think its timing, then probably best left to a service technician to repair.

simpliest thing could be that the needle is in backwards - check it - flat shank to the back.

Or timing is out, ie. when the rotary hook goes around it needs to be timed to when the needle is at its lowest point so that the hook catches the thread at the back of the needle.

Has it jut happened after a jam up/rethreading ? If so, rethread everything, new needle and try again.

If no change to lack of stitching then sounds like timing is off - generally means take it to a professional for repair.

Have you changed the needle since you purchased it? A needle should be replaced every 4-6 hours of stitching so for each garment sewn as a rule of thumb. So try replacing the needle, cleaning and oiling the maachine as per the manual. Check needle is in the correct way, it is easy to put in backwards if you aren't familar with them, flat shank to the back and there is usually a scarf (cut away area) at the back of the needle which is where the rotary hook under the needle plate comes around to catch the upper thread during the stitch process. So if needle is in backwards this will cause stitching to fail.

So elimate the needle firstly.

If this fails and the knocking noise continues, then it could be that the timing has been knocked out. It can happen if you sew over a pin and hit it hard (or the needle strikes the foot if stitch setup is wrong for the foot being used). In this case, you'll need to take it back to the shop for the serviceman to fix.