Superpot,
I can give some response to the latter part of your question, based on my recent experience. It may or may not help any with the grinding noise ...
The pivot plate adjusting screw is used to adjust the variable speed mechanism to produce a spindle speed that approximately matches the speed shown on the dial. After doing a partial rebuild on my 2J2 head, swapping out some parts, I found that the pivot adjusting screw - which I had left in the same position in which I received it - was giving me a spindle speed approximately 2x what the dial indicated.
To measure the actual spindle speed, I bought an inexpensive photo tachometer similar to this:
Amazon.com: Digital Photo Laser Tachometer Non Contact Tach RPM Meter: Automotive. (IIRC, I bought mine on ebay for considerably less, but longer shipping time.) By testing it on known rpm devices, I found this inexpensive tachometer to be quite accurate across a very wide range of speeds.
Unfortunately, when I adjusted the pivot adjusting screw downwards to correct the speed, I began to hear a scraping noise at certain speed settings - apparently, the pivot plate was not quite clearing the pulley. This might be due to the fact that I had swapped out the pivot plate that came with the machine to a different pivot plate - because my pulley needed to be re-bushed, and a member here offered me a great price on a rebushed pulley with the pivot plate and new bearing already assembled. Perhaps this "new" pivot plate is slightly different from the old one ... but regardless, I found that I just could not dial in the rpm range without parts scraping against each other. As I tried different adjustments, I found that in some positions I would get the scraping at the lowest rpm, and in other positions I might get scraping at the highest rpms.
One obvious solution would have been just to find a position for the pivot adjustment screw that resulted in no scraping, and then just know that I needed to convert the speed shown on the dial to the actual speed. But this still left me at a much higher speed than shown, meaning that my lowest speed was no longer 60 rpm, but more like 100-120 rpm. I don't know if I'll ever need the low end, but ... I wasn't satisfied with this solution.
On closer inspection, I realized that there was significant wear on the two pivot bushings and even more on the pivot area of the adjustment screw. I made new bushings and a new adjustment screw, hoping that would help me get better results ... and it did, much better. Now I have been able to dial in the speed so that the rpm shown on the dial approximately matches the spindle rpm, and I have no scraping throughout the full adjustment range -- except for 400-500 rpm in back gear. "One of these days" I'll get back in there and see if I can ease whatever it is that is scraping, but for the moment, this is more than good enough for me; basically I have continuous speed adjustment from 60-400 and from 500-3000 rpm. I can live with the jump from 400 to 500 rpm! Here's a link that gives a bit of information:
http://www.practicalmachinist.com/v...-2j2-speed-adjustment-plate-okay-weld-338817/
I don't know how much, if any, of this will be helpful to you, but hope it might give you some things to look at ...
