So I went on the internet and searched and searched for information on how to repair and set the timing on a serger. I did get some help from the nice people in the alt.sewing google group but basically there is no information on the web on how to repair a serger. There also seems to be a lack of books, or even classes on sewing machine/serger repair. I don't really know how a person becomes a sewing machine technician. I assume they must learn the ropes through some sort of apprenticeship. I did get a "Generic Serger Manual Service and Repair" for x-mas but it is basically a photo copy of some info from the 80's and is missing some relevant pages. Plus it isn't really generic, it is basically some notes for some various older Singer sergers. However it did give me some good hints that let me figure out how to set the timing.
So I think there is some kind of conspiracy going on. Considering that the local repair shops charge $100, it becomes very pricy to get your machine(s) serviced every year as recommended. Especially if you have machines that only cost around $100-$200. Maybe the sewing machine manufacturers are trying to keep the relevant information secret so you feel compelled to buy a new machine when yours breaks. I don't know.
I have a Kenmore 385.1664190 serger. You can get schematic pictures of all the interior parts, and order any possible part by going to the sears parts website and searching for your model of sewing machine or serger. However they do not offer a repair manual or tell you the specific placement of the loopers for timing. But the schematics helped me figure out what screws might be loose.
In my case both my upper and lower loopers were loose. So the upper looper (top red arrow) was wiggling forward and backward. And the lower looper (lower red arrow) was wiggling left and right. To tighten the upper looper I needed to stick an Allen wrench (the green thing) in the hole shown. If the lower looper is loose on the shaft you can use the screw that the blue arrow is pointing to, and I assume you can also use this screw for fine adjustments. But in my case it was the whole shaft that was loose (not the looper), so this screw didn't help me plus it was really hard to get to.
So to tighten the lower looper I needed to open up the bottom of the serger. There were two screws on the bottom plate, plus 4 screws in each of the rubber legs. The picture below shows what the bottom of the serger looked like. Once again I needed an Allen wrench to tighten the two screws where the red arrows are.
So now you need to know how to position the loopers so they actually do something.
Basically when the needles are at their highest position, the upper looper should be underneath the needles if you are looking straight on, but slightly in front if you are looking from above. If you had a repair manual I think it would tell you exactly how far the point of the upper looper should be in comparison to the left needle, and it varies from machine to machine. My generic manual was missing this information for their sample (Singer) machines. It did say that on the sample machine the looper should be 1mm in front of the needles.
The lower looper seems to belong exactly horizontal.
When the needles are at the lowest point the lower looper is supposed to be a certain distance from the left needle, for the sample machines it was 7mm. I had to guess on my machine. The needles do pass between the little pinchers in front of the looper.
When you rotate the handwheel the lower looper and upper looper's will pass very close to each other, they almost seem to fit together like a puzzle. There is probably a specified distance for this as well. The picture below isn't that great. Just think puzzle pieces.
Sewing machine technicians have exact measurements for where the loopers are supposed to be positioned in relation to the needles and each other, but this doesn't seem to be freely available information. So if your timing hasn't been disrupted too much hopefully the above information will be helpful.
If this article helped you and you would like to offer monetary reciprocation I would gladly accept paypal donations, or amazon.com gift certificates. Even a dollar would be nice. ;) Thank you.