I've been told that the Polyester thread is made from many short strands,so if you use it where it rubs against something like the inside of a belt it pulls some of the strands off the thread giving a fuzzy look after a while.Nylon doesn't do this since the strands are alot longer & stiffer.
This is one of the many ways it can skip.But it's better to look for things like this before you start turning wrenches.
Lower the needlebar all the way down & make sure the spring is pressing against the thread like it should,once in a while a piece of thread can get caught in there & hold it open,sometimes they just get bent & need to be replaced.Also do you have enough pressure so the leather is being held down?
You should be able to sew up to around 20 oz for leather BUT this machine does NOT have needle feed,it has feed dogs with teeth that will mark the bottom of the leather & it also has teeth on the bottom of the feet.But they can be ground off so you won't get feet marks on top.
I've had 2-calls in the last week from people that bought one from Tandy & they both want to trade them in.They won't sew heavy enough & are marking the leather.I was nice to them & mentioned we do not have a market for this machine & don't want it on trade.They weren't very happy about it & now are probably upset with me since I won't bail them out.I'm willing to bet in a few more months Tandy will stop selling them.They are better suited for sewing vinyl for upholstery,sails or tarps.
It is the one in the back where the rod comes out which has the sliding walking foot adjustment on it,the cam is inside the head on the top shaft & has 2-screws in it to loosen so you can rotate it on the shaft.
Sounds like a lot of fun.Yes,the wicks you have will work.On the Singer you have to mill down the top of the hook basket so much that you hit the screw that holds the upper bushing in,if you got a different hook saddle from a Consew or Juki a large bobbin will work w/o any work but you will still have to mill the small bobbin one from either brand.
IDK how many times we tried different bobbins from different suppliers for the 1541 & finally found some that are consistent.The black steel ones seem to be the worst.
Make sure there's no play in the feed cam,there's little screws & you can adjust it with,be sure to unlock them first with the locking screw,if you get them too tight you won't be able to change the stitch length.
I would guess someone had the handwheel off & didn't put it back on the groove where it should be ,easy fix.Loosen the handwheel screws (down in the belt groove) & re-install.
Sometimes in this type of machine w/o a walking foot the stitch length will shorten if your sewing leather,put a piece of paper or cardboard & see if it gets longer.
I would say keep them all for now too & maybe a few years down the road you'll be able to better decide which one works best for you.You shouldn't have any trouble getting them in a room that size either.
Keeps the head from jumping around while your sewing fast.As much as this weighs I doubt if it'll happen,they way it's setup the belt would hold it down.