Singer overlocker keeps skipping stitches

[Fair-Stumped]

My Singer overlocker keeps skipping stitches. I've tried all the suggestions in the troubleshooting guide but it still skips. I've changed the needle, made sure the needle is securely in, increased the pressure foot pressure, rethreaded it loads of times and messed about with the tension loads too. I've run out of ideas.........grateful for any other suggestions. Thanks

[boxtops]

Have you checked the tension? I've never used an overlocker but with the sewing machine, if the top and bottom tensions don't match, the stitches can get very irregular.

[Mosaic]

Has it sewn successfully before? Just an initial thought.
I'd go back to basics with the fabric you're using - as tensions differ for each fabric type.
Start off with say 3 on all the dials - do a trial. You need to be able to identify all your threads s might help to use different coloured spools at this point. Look at the line of stitching and from you will see whcih threads need tightening, and so work through it until you arrive at the solution for the fabric in question.
Also, if it is a sheer fabric, most domestic machines skip. Consult your user manual for advice - let us know how you go on.

[Fair-Stumped]

Thank you both for your thoughts. When I bought it 2nd hand I got it serviced before I started off and it worked beautifully. I've tried altering the tensions in the way you suggest Mosaic, as I hadn't been so methodical before - it starts off looking fine and just as I think I've cracked it, it skips. I'm working with a drill weight polycotton and I'm wondering if I need a different needle - I'm using a 90/14? I'm also wondering if the timing has gone a bit wonky but then that wouldn't explain how it can work fine for a few inches and then skip.

[Mosaic]

It might be worth trying an 80 needle.
This link suggests it could account for skipped stitches;
http://www.singermach...ine-missing-stitches/