When I thread and use Three thread cover Stitch the right hand needle thread continously breaks while sewing I've changed the tension and no joy I was sewing hem on leasure wear

The 335 has a two thread chain stitch (stitch type 401), and the overlock side (right needle side), is a three thread plain overlock. If you are describing the plain overlock as the problem, I would first suggest the following in re-threading:

1. Thread the upper looper
2. Thread the lower looper
3. Thread the needle last (important)

If the needle threaded, you cannot re-thread the lower looper without breaking the thread.
In order to thread the lower looper, the lower looper must pass by the needle thus picking up the needle thread. So, instead of threading the lower looper thread underneath the needle thread, the looper would be threaded on top and cannot sew without breaking the thread.
Make sure that the threads are bedded between the tension disks. Check this by stretching the thread fore and aft of the tension disks as well as visually noting that the threads are not accidentally threaded behind the disks. You can also loosen the tension disks when threading so as to allow the threads to bed deeply between the disks.
Please reply with your observations.

try changing the needle first--make sure the needle is the correct one for the fabric being sewed.
if you've adjusted the top tension & the bottom stitch still looks the same
it's possible that the top tension dial is needing to be checked to see if it's
working correctly

Rolled hemming on any overlocker is usually achived the following way. Right hand needle only.
Blade over to the right usually to cut wider than normal but you can vary this to suit the fabric and stitch width you want.
Thread in this needle and the upper and lower loopers. If you can source any, use woolly overlock thread in the upper looper, this fluffs out when not tensioned and covers the fabric to give the look of solid stitching. Change upper looper tension to about 2 and lower looper tension to about 6 or 7.

The lever by the plate is usually to control the little stitch finger where the stitches are formed, move it backwards and it should move back towards you?? If this happens, then you want it in the retracted (towards you) position for rolled hemming so the stitching is much smaller and the fabric can roll. Normally this stitch finger holds the fabric firm for the loopers to form the stitch over for your normal 3 or 4 thread overlock.

Now test stitch and see how it looks. Tighten the lower looper thread so it lays right beside the needle on the underside. You may need to then tighten or loosen more the upper looper, you want the upper thread to wrap all the way around to the underneath against the lower looper thread and needle.

The cut edge of fabric should roll to underneath inside your seam. Once you've got this happening, turn the stitch length down to 0.5 or so to close it right up tight. This uses heaps of thread so I usually test everything else, then close it up at the end to minimise waste.

Hope this makes sense, good luck.

Are you sure you have got the top thread threaded correctly including the take up lever? Start at the thread spool and follow the thread all the way through the thread path checking that it is not snagging on anything enroute and that the thread is correctly through the tension device. Also tension dial should be on 4-5, if its higher this could be breaking the thread. YOu should not need to adjust top thread tension more than a half increment at any time.

Other possibility is that the bobbin holder under the needle plate has moved out of alignment and then the top thread is catching there as it goes around the hook.

If you check your manual it should give you instructions on removing the needle plate (2 screws need to come out), then you can lift the bobbin case out towards you, clean underneath with your little brush, then reinsert it. There are two little red marks on the right side of the bobbin case and a stopper, these need to be lined up. Then put in bobbin and rethread into tension spring, replace needle plate, bobbin cover, and test stitch.

Hopefully one of the above is causing the thread to break.

Just trim the fabric to the desired hem length plus one inch, then overlock around this raw edge with thread close colour match to the fabric.

You then have the choice of either stitching around with a stretch stitch on your sewing machine, or hand sewing.

Being lycra shouldn't change how you hem them unless the trouser leg is extremely close fitting and the hem seam is going to be under tension.

My first choice would be using a twin needle in straight stitch from top side but this finish can pop/break if the hem is under tension. But perfect for most knit hems.

If you hand sew then you can turn up hem allowance and put a length of fusible hemming web inside the hem allowance and press it to hold. Then do a back stitch hand sew around to hold hem in place.

If you sew with the regular sewing machine, then use either the stretch stitch or a very small zig zag, and a ball point or stretch needle.

On ready to wear you would see a coverstitch hem but your overlocker doens't have this stitch.

How frustrating, I've tried to find a manual on this model so I can see how you make the change to the thread finger on the throad but couldn't see one. So, I'll go through the set up for 3 thread rolled hem on mine, it probably won't be identical but it might help.

First, remove thread from left needle and remove the left needle from the holder leaving just the right hand needle in place. Most sergers have two seperate needle screws so this can be done but as you mentioned, recheck again that the right needle is right up into the housing as high as it will go. I presume you are using a fresh smaller size needle, especially if this is on a fine or lightweight woven like organza, I'd put in a size 70. If a mid weight then size 80.

Now there should be a thread finger on the foot you change with your screwdriver. Or a little switch you flick so that the throat plate is a different shape to form the narrow seam. Your manual should have this step.

Now if you have some, put wooly overlock thread into your top looper, I cut the thread about 10 inches above the tension dial, put the new spool on, knot it to the existing thread tail, turn tension to zero and pull it through and through the looper eye.

At this point, you should have the two looper threads loose, lift the pressure foot and pull these two threads under the foot and out the back. Turn tension back to about 3 on top looper and tighten up lower looper to 5 or 6 and leave needle at 5.

Adjust blade to cut quite wide, ie wind it to the right side. Now thread the right needle and pull this thread out the back too. Lower the pressure foot, introduce a piece of fabric in under the foot, press the pedal and start trimming and chaining off.

You should have a chain stitch happening now - if not, recheck your threading, particularly the needle, sometimes the thread looks like its in the needle eye but is hooking around the looper. If you still can't get any joy, then it is possible that the timing is just slightly out and this is affecting this stitch. You could try setting up for a normal three thread seam and see if this chains okay.

If you are getting a chain happening now, then adjust down the stitch length to make it denser so it is covering the fabric and check the underside, adjusting top and bottom looper tensions so the thread is enclosing the fabric end rolling to the underside and covering any little fibres.

I hope this is of some help - however, if it still isn't giving you a chain, it could be the timing is out in which case, unfortunately service time.

read the manual and go through the needle threading and bobbin winding procedure step by step as if you were a novice. I believe the bobbin is ether wound or installed backwards.

If the thread is shredding and breaking, there is an incompatibility of your needle, thread, and fabric. Could be old, bargain bin, or poor quality thread--does the thread have little "hairs" of thread lint sticking out of it--that's probably not good quality. Look for fresh, good quality thread. Try a brand new needle--a sharp if you are sewing woven fabric. Make sure the thread is not too big for the needle eye. Sometimes, a top-stitch needle or embroidery needle will work well on FMQ. (A top-stitch needle has a longer scarf which helps protect the thread during the multiple times the needle penetrates the fabric before the thread forms a stitch. Shredding means the thread is getting worn out before it forms a stitch. A piece of thread penetrates the fabric 10-20 times before it forms a stitch.) Could also be a snag somewhere that is damaging the thread.

Sewing Needle Troubleshooting Guide

SCHMETZ Household Needle Chart

Most FMQ instructions say the upper and bobbin tension should be the same, however, I find my machine works a bit better when the bobbin thread is just a little tighter than the upper thread. Then the bobbin thread does not "pop" up on the top of my fabric quite as much. It's probably something you will just need to experiment with in getting used to your machine.

P.S.--when threading your machine, make sure the Presser Foot is ALWAYS RAISED so the top thread will seat properly in the tension disk. Failure to do this will cause thread barfs (usually referred to as thread nests or bird nests) under your fabric. Also, before beginning your FMQ, ALWAYS PULL the bobbin thread to the top of the fabric, then hold both thread tails gently in your left hand while you slowly take the first couple of stitches.

How and Why to Bring up the Bobbin Thread

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If it was sewing correctly BEFORE the needle break...why did the needle break in the first place?...and what fixes did you make?
If it sewed properly...what changed?

Cut your upper thread close to the spool...make sure the presser foot is raised and pull the cut off thread section through/out of the machine from the needle area (sewing direction...do not pull the thread backwards!)

Clean out the bobbin area...remove any traces of lint or pieces of thread...look for any broken off needle pieces... brush the bobbin area out....then add a drop of sewing machine oil (but only if your manual says to oil that area).

Remove the needle plate to expose the feed dogs...brush/clean out that area too and add a drop of sewing machine oil...then secure the needle plate back on.
Replace the needle...do it again...yup...some needles arrive bad from the factory. Make sure the needle is inserted and positioned properly. Then thread the machine WITH the presser foot in raised position. (The thread needs to get seated into the upper tensions.)
..with the.presser foot down...thread the new needle.
Oh...and use the correct needle for the thread. (a universal 80/12 is standard).
Thread can cause issues too. Try a different bobbin, or maybe a different spool of thread to see if that makes a difference.

1) It’s possible the machine is threaded incorrectly. Remove the thread completely and rethread the machine. Be sure to use good quality thread--don't buy the cheapest you can find. A good thread will help your machine perform better and your projects last longer.

2) Poor stitch quality can be caused by the needle. Make sure you're using a new needle that's right for the job. Many times machines are taken in for repairs and all they need is a new needle. If you can't remember the last time you changed the needle--it's past time. Needles should be changed at least every eight hours of sewing.

3) When inserting a new needle, make sure the flat side of the needle faces away from the bobbin area. For example, if your machine has a frontloading bobbin, the flat side of the needle faces the back of the machine. If your machine has a side-loading bobbin, the flat side faces the right side of the machine. Some older sergers require special needles that don't have a flat side. Refer to your owner's manual to properly install a serger needle.

4) Thread that shreds or breaks can be blamed on the needle. Use a good thread and make sure the needle eye is large enough for the thread type. Also use the right type of needle for the fabric;
5) The machine tension adjustments put stress on the thread so it doesn't simply flow through the machine. When the upper and lower tensions are balanced, the stitch forms correctly. Tension is easy to adjust--stitch on fabric samples with a different thread colour for the upper and lower threads. Observe the stitch, adjusting the tension until the stitch is formed correctly. As a general rule, adjust the upper tension first. If the stitch still isn't right, adjust the bobbin tension.