Alternator varnish

[Kthomas55]

Any thoughts on sealing off the windings on CB77 alternator. Varnish or some type of spray ?Impregnated paper has degraded . Also anyone know the testing procedure for alternator off the bench . Resistance between wires or ?

[Kthomas55]

No one has ever done this ?
I thought about epoxy but after reading data sheets it looks like it wouldn’t be compatible with oil

[Tim Allman]

The wire that forms the coils is coated with a varnish that provides the insulation necessary to separate the coil windings from each other. Motors and magnets are usually built the same way. The outer wrapping material is there just for physical protection. Whatever material it is made of seems to have been a poor choice because of its lack of durability, especially when covered in motor oil or perhaps chain lube.

So, as long as the varnish is not damaged in the process, I think you have a lot of choice in materials to use. You could also do nothing given the generator is completely protected with the covers in place.

As for bench testing, you would have to recreate the engine setup which a) would be a lot of work and b) you already have. You could check for connectivity with an ohmmeter. All of the coils are connected at one end so there should be a low (unspecified) resistance between any two of the wires and no connection to ground.

If you PM me I'll send you a scan of the shop manual which shows a wiring diagram and discusses the generator.

[DJM]

I had the same problem when I restored my CB77.

I used an ordinary epoxy, Araldite if I remember correctly, not the quick setting variety.

Mix it up a bit on the thin side nd then just brushed it on with a cheap kid's painting brush.

It's worked well on both of my bikes, no problem with oil, in the case of the CB77 engine the alternator runs in air anyway, not oil. 10,000 miles plus with no issues.

I thought that I had the coil resistances recorded somewhere but can't put my hand on them.

As a guide, the brown wire is common, resistance between brown and yellow should be about twice that between brown and pink, quite low values so remember to subtract the resistance of the test leads. If your values come close to that you will have conductivity through all of the coils so all should be well,

Good Luck.

[Seadog]

CRC Seal Coat, an electrical & electronic non-conductive polyurethane film.

[Kthomas55]

Thanks guys
There are spots where the paper is gone on mine but it seems to test out ok

[Kthomas55]

I took it to a local guy that fixes electric motors and he said he would dip it in whatever type of varnish he uses and then bake it for 4 hours. He has other things he can do at the same time.