Whew! For a second there, I thought I had a metallic paper. Silicon Carbide, I should be fine. The only thing I could find was a Wet/Dry sandpaper (http://3mauto.com/products/abrasives...3020-p600.html), and I thought that was some sort of metal oxide. Perhaps it was back int he day... *shrugs* Thanks for the warning!

I had a 401 with a motor that would run freely, then with the load of the machine it would drag. I was certain I had the machine cleaned and oiled properly. So I changed the motor from a nicely running machine and it would run then start to drag. So it was not the motor. I re-serviced the machine. nada. Finally I laid the machine on it's back and oiled the throat plate area/feed dogs again and ran the machine while it was on it's back. All of a sudden the machine started running zoom zoom. go figure. All it took was one little spot of dried up oil in some small spot somewhere.

I remember that machine :)

In this case though, I can move the motor from machine to machine, and each machine it's on suddenly develops a "problem" running. Change back to the original motor and the machine is fine again.

Small motor repair is a fascinating subject. The techniques described above will cure most ailing motors but if my memory serves there are a few where a small motor repair shop testing equiptment is needed to diagnose. Wish I could be more specific about the "advanced" testing techniques. I've had a couple motors like you describe and after trying everything they still were a little slow. I'm real curious as to what exactly ailed them (though I believe the windings were bad) but can't say for certain. Good Luck.

Jon

OK,.. I'm terribly sorry I left this thread so long.

Here's what we did:

Motor 1: Do Ohm test on the commutator (passed), clean the commutator, and re-assemble to see the result. With a very loose belt - just prior to slipping, as Singer recommends, virtually no more growling and excellent speed and piercing power on the 201 it came with.

As a note, the symptoms that this one had according to this document: http://www.morganamt.com/gb/files/Mo...r%20patina.pdf were: Slot Bar filming, Patina streaked with Collector wear, and grooving.

This makes a lot of sense, based on the shape I got the machine in. It looked like it had lived and worked in a barn most of its life.

DH did the sanding, I did the reassembly and testing.

Motor 2: Do Ohm test on the commutator (passed), clean the commutator, and re-assemble to see the result. With a very loose belt - just prior to slipping, as Singer recommends, still growls on startup, and stops very easily on the 115 test machine.

The belt was an old belt, and felt somewhat tacky, vs the harder and relatively smooth new belts. No amount (or lack) of tension on the belt could stop the growling. Additionally, the motor would "jam up" from time to time, causing it to not start without a fair bit of force turning the handwheel for about a half turn.

I removed the motor from that machine and installed it on the 201, with the new belt. It performed excellently. I checked the 115 again, but it spins freely, and exceptionally well (like most "treadled" heads of the era that I've come across.)

Then, I thought I'd change the belt just to see if the belt was too tacky. Looked at the number on the belt: 196388. Huh? That's not the right belt. Pulled a 193066 and installed it. The new belt is ever so slightly longer. In fact, to remove the old belt, I needed to remove the handwheel. The new belt could be installed without removal.

Growling was virtually gone (the smallest low pitched hum was noticeable on start, but that's it.), machine could start on its own (without needing the handwheel turned manually to start) and piercing power excellent, all symptoms of "jamming" disappeared.

The symptoms that this one had: Slot Bar filming, and heavy Patina streaked with Collector wear. This was surprising, because it was the newest motor of the ones that we have here. It looks like it was bought as an "add on" to the machine I purchased it with (a 1912 28). Notably, the wiring was thinner, and looked more poorly put together, and the bearings were "greaseless" (no grease pots at all on the motor). It's also one of the few motors that have come into the house that didn't require the wiring replaced.

Theory: It was a combination of the commutator needing some work, and the belt being the wrong length, causing some sort of leverage issue, especially combined with the heavier handwheel.

Motor #3 (Bernina): Time of death - 4:10pm May 20, 2013.

(Possibility of resurrection, if I can can get into it, but between the two of us, we had to be missing something, because we couldn't get in to service it.)

Symptoms on the commutator: Slot Bar filming, Extremely heavy Patina streaked with Collector wear, and grooving that looked more like it was cut in than worn in. This makes sense, since the lady had complained that the motor didn't work, and that it had been running slowly for some time before it stopped. The original brushes were worn to nubs, and this is after a supposed service by a professional shop.

When I got the machine, it was pretty much seized solid. I could barely turn the handwheel and it took 2 hands to do it. Today, it turns well, until it hits the huge crack in the cam gear. Then it spends its energy trying to peel the gear apart.

Looks like I'll have to part it, or sell it for parts. It's a shame though. It's got probably everything it ever came with from the factory with it. :(