What is this part?

I've been doing some work on my 82 xj650 Maxim, and today when I went out to start it, it will crank for a while, and then it sounds like a grinding noise coming from this part. I took off the cap, but I cannot identify what function/part this is, and if it's supposed to be as grimy as it is. The image is attached below.

 

That is the alternator. The grinding noise you hear is from the starter clutch, which is directly behind (but not accessible by removing) the alternator,
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What state is the battery in, and has the starter been rebuilt?

Check the length of the alternator brushes while the cover is off, and clean up the copper traces on the alternator with an eraser.

 

That is your alternator rotor and stator the two copper rings on the rotor have carbon brushes that rub against them (Brushes are housed in the cover you took off).

 

The battery is actually brand new, came in the mail yesterday, charged up overnight and installed this morning. I haven't done anything to the starter, except I cleaned both terminals real well, as there was a bit of corrosion. And the brushed are about 7mm and 5mm.

 

The service limit for the alternator brushes is 10mm, so those will need to be replaced.


Given that you found corrosion on the starter terminal, I think it's advisable to refurbish the starter.
Replacing your starter motor brushes w/ pics

The one bugaboo about the starter clutch is that the cases have to be split in order to repair it, so the goal here is to eliminate all other possabilities that can cause the starter clutch to slip in order to (hopefully) avoid splitting the cases.

Start a conversation with chacal for parts. He has the correct parts in stock.

 

Thanks, much appreciated. I'll reach out to him, get the parts, and follow up on here afterwards. Side note: @k-moe love your profile picture. I consider The Big Lebowski to be my favorite film of all time. The dude abides!

 

If you're going to be going through your starter the positive cable will be disconnected anyway, I would advise taking a meter and checking the resistance of the positive cable from the solenoid to the starter. There's a good chance it's fine, but should you find extra resistance in that cable it will still effect the starter whether it's rebuilt or not. I just figure it's a simple test to make sure it's good. I think you are being steered on the right track. Kmoe is very knowledgeable