When I first started using my Serger, I was loathe to change the threads to different colours. If you've ever had to rethread an overlocker, you know what a super huge pain it can be. Tiny little holes way deep in the machine and there's usually three or four threads to do. Mine needs some long handled tweezers, a sharp pair of scissors and heaps of patience. Somewhere along the way, my mum tipped me off that there's an easier method. Thanks Mum!
1. With plenty of slack, using an overhand knot, tie the new threads to the old.
2. Make a note of your current tension settings then reduce them all to zero.
3. With the presser foot up, slowly pull all the threads through the machine. You can also put the foot down and use the pedal to run them all through, but you have to go slow and make sure the knots don't get caught anywhere.
4. Stop before the knot makes it to the needle eye. You're going to have to rethread that one by hand. Most times the knot won't go through and you'll either mess up the rest of the threading or bust the needle. Whoops!
5. Reset your tension and you're finished. Quick as a wink and no tweezers required.