bobo383 wrote on 12/31/69 at 16:00:03:Mine had the thick one originally, but I used the smaller ones when I was playing with the jetting. It still has a smaller one in it. It fits and holds the washer in just fine. Appearance is different, but it works.
FYI - My nearest bike shop only had Keihin jets - they work and fit, too, and look like the smaller picture. The numbers are not the same, though. a 155 Keihin was about the same as my 145 Mikuni. Mikunit is in it now, a 155.
(I measured the jets with drill bits - NOT turning at the time. I know it ain't exactly right, but it worked for me)
As a point of interest and if you are drilling out your jets with micro drill bits rather than purchasing four of the same size each time!
The Mikuni jet sizes are denoted in tenths of a millimeter and increase 2.5 tenths of a millimeter per size. i.e. a #155 main jet is actually 1.55 mm. diameter, the next size up(adding 2.5 tenths of a mm.) is a #157.5 main jet, which is actually 1.575 mm. diameter, and so on.