PABOH,
The HP issue has been beat to death on this forum, but not for a while. When this issue rears up again, sometimes those of us that have been around a while feel like we are revisiting an old argument. Yet for you, it is new and we really shouldn't beat you up too bad. /forums/images/graemlins/blush.gif Buck has sold hundreds of these tractors, and I'm probably being conservative. He is right, it is clearly not KW at the PTO.
One way to study this is to look at the few almost dead on models produced for both Japan and the USA. There are quite a few cross over tractors, meaning they were sold here and there as the same basic tractor, or at least with the exact engine. The Yanmar YM2000 in Japan is rated at 20HP, while it's nearly identical USA twin, the YM240 is rated at 24HP. The YM135 Japan (13.5) and the YM155USA (15.5) is another example. The John Deere 990 and the Yanmar US35 is another. In all these cases, and many more, they are rated real close to 20% higher in the US than in Japan. The common rule respected by experienced dealers is that the rating on a xx Japanese tractor is xx times 1.2 in the USA. It is thought the Japanese rate the usable PTO HP in their model numbers, and the USA market likes the higher flywheel number. Years ago I held the kw theory also, but a little study has shot that down.
I have a PTO dyno. Buck probably does also. The PTO rating theory works on the dyno, the kw is no where close. I guess that says something.
I used to import from Japan. I've moved on to new tractors now, but I can't help jumping in every once in a while.