So I joined the group, and spent about 30 minutes browsing the site.. I now understand why I've never heard of groups.io. that seems to be the most convoluted and impossible to navigate site I've ever visited lol.
You should seriously consider a different host for the forum, maybe even just integrate a Google drive folder to a basic forum.
After about a half hour of searching, and being unable to find a single technical document on any tractor, other than an Excel sheet that was supposed to list specifications of tractors but for some reason only cataloged horsepower ratings, I gave up.
I should note: I'm a computer programmer and web developer - I build my own computers, I design and build automated machinery and robots, write all my own software, design all of my own electronics, build on my own circuit boards, fabricate all of my equipment using CNC, 3D printing, my old school DeWalt sliding miter saw, a welder and some grinders. I should be able to figure the site out lol.
That's a shame, because according to your post there is a plethora of information there that I have not been able to find anywhere else.
I did however, find that
www.southernfarmequipmentimports.com has the Japanese versions available to download for free.
Here is a link to their 1600/1900 listing:
CLICK ON THE PICTURE OF THE TRACTOR BELOW OR CLICK THE LINK BELOW TO OPEN MANUAL. ***YOU DO NOT HAVE TO PURCHASE THIS MANUAL TO DOWNLOAD IT*** https://cdn.shopify.com/s/files/1/1486/5356/files/YM1600_YM1900_PARTS_MANUAL.pdf?v=1664565805 **THIS IS A FREE PDF DOWNLOAD MANUAL YOU DO NOT...
www.southernfarmequipmentimports.com
Here is the ym1600 service manual direct download link provided on that page:
Hope you guys get that worked out, and thank you for all of your hard work from all the people that were able to figure your site out. Cheers.