Where can I buy a presser foot for a riccar model rl343dr this is a overlock machine Thank you

Sorry to say, but usually misthreading is the culprit. The machine must be threaded "each thread" in the correct order (usually upper looper first, then lower looper) and following the correct threadpath. Also, the presser foot should ALWAYS be raised when threading. Give each thread an extra little tug (grasp thread below the thread tree and also below the tension disk) to make sure it seats completely.

Verify you are using the correct needles for your machine. Some needles vary by a fraction of an inch but will make a big difference in serging success.

Remove all the threads from the machine.
(Always cut the threads below the spools, raise the presser foot, and pull the threads DOWN through the needles--Never pull up!)
ALWAYS RAISE the presser foot when threading.
Be sure to always thread each thread in the proper order--threading out of order will usually fail.
Rethread from the beginning and give each thread an extra little tug when threading the tension disk.

If a thread breaks, it is usually less frustrating in the end to remove all the threads and rethread from the beginning. Trying to rethread a broken thread will most likely cause problems.

Presser foot or foot control?

Search for:

Make Model presser foot
or
Make Model foot control

Search the internet for:
Riccar sewing machine presser foot

http://www.sewingpartsonline.com/riccar-sewing-machine-parts-model-list.aspx

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Perhaps the manual would help:

Empisal Overlocker 760C Empisal Sewing Machines

On most machines, it is important to ALWAYS raise the presser foot when threading the machine (although the instruction manual says to raise the presser foot only to pull the thread tail under it). Be sure to give the thread an extra little tug when going through the tension disk to seat it properly. Be sure to thread in the order as specified (Upper looper, Lower looper, Right needle, Left Needle). If the machine messes up, it is usually a best policy to remove all the thread and rethread from the beginning. Threading out of order will almost guarantee failure!!!

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Try this site or search the internet for:
Toyota 6600 presser foot

Presser Foot Toyota White 11932

...

Both.

http://www.sewingpartsonline.com/riccar-sewing-machine-parts-model-list.aspx

If they don't have it showing online call and tell them exactly what you want. They may have them or can order them for you.

check with
sewvacdoctor.com
a1sewingmachines.com

try www.icanhelpsew.com