So for reasons I don't think anyone knows the SP Shock isn't particularly serviceable. I bought an SP shock to be the final piece of the puzzle in converting my R model to an SP model. But the nitrogen seems to be a little low (shock reservoir cap can be pushed in about 1mm). Nonetheless, I would like to add a schrader to check the pressure from time to time. I was thinking of doing two things:

Adding a schrader valve however not sure what the best approach is: threading a valve into the cap and/or welding a nut to reinforce the area around the valve

OR

Use the shock reservoir off another bike, probably an 80s CR125 or CR250. From my understanding, the SP Shock is different to other shocks in the design of the reservoir however I'm guessing the threads would be the same in the reservoirs for the oil line. I guess this would also change the settings on the shock too.

Anyone have any advice on which to do? Ideally I would just get an Ohlins shock however with the US dollar recovering, an Ohlins shock is nearly as much as what I paid for my NSR and the OEM SP Showa Shock was 10% of the price. I think the seals are good as well.

Also, the spring collars seem to be quite stuck but I'll tackle those another time.