I think that's the manual transmission version of YM187, so the numbers in the YM186 brochure should be about right.
284 International
posted a link to the brochure; originally provided by rScotty.
This YM186 brochure shows 3-point rated capacity of 661 lbs at the lift pins, 529 lbs at (industry standard) 24 inches back from the pins.
Note you will need a lot of front ballast to lift that much - without the ballast the wrong end of the tractor lifts instead.
Here's an example of ballast on my YM186D, about 250 lbs ahead of the front bumper. I can lift my disc, spec about 650 lbs, but the steering is so light I have to steer mostly with the brakes.
Added: going to 284's link, I see he also has the YM180/187 brochure online. (Look down the left column of his index).
That YM180/187 brochure shows 1036 lbs at the pins, 836 lbs (? - illegible) measured 24 inches back. I have a hard time believing these figures are credible when the weight of the YM187 is approximately the same as YM186. If credible, they must have a huge amount of nose ballast added.