This is a good instrument, and has become a favorite of school programs in our area. Band directors have been pleased with the intonation. I like the sturdiness of the key work. The instrument has the headless pointed pivot screws, so extra wobbles can be eliminated.
Bore: 14.9mm at the top of the left hand keyed joint, 14.6mm at the lower end of the same joint. This bore size is why the low B-flat and A are sharp.
So it looks like Yamaha used a Bundy or Selmer Signet as their model.
Left hand key work also looks more like Selmer or Buffet.
Low intonation is good. Testing is with an F scale, and I was pushed in all the way. In the display below, some other notes are just blips. The display starts on the left with low E. The throat tones are not too sharp. The low B-flat and A are the notes that would be too sharp. This is typical of student horns.
High register intonation is good. Here I played an F scale but added both B naturals. The clarion E is too sharp, but I didn't play it long in this sample. The upper register is not too sharp.
Pulling some at the barrel, and perhaps a bit in the middle, will give very good intonation for this horn.