The Monza Jr. came from the factory with 16" wheels. The 125 Sport used 17"wheels. The 125 F3 and 250 used 18" wheels.
I decided to go with 17" wheels because I want the bike to look like it's a smaller scale than a 250. Also, people on the bevelhead list have reported that 18" wheels are a tight fit on a Monza Jr.; the swing arm is shorter than a 250's and the rear tire may hit the fender under some conditions. Now that I have the 17" wheel and tire in place, I'm wondering if an 18 wheel would fit at all with this fender. The 17" barely clears at full compression. I was cautioned by Frank Scurria that using 17" wheels would let the pipe touch down that much sooner in turns, but for a hacker like me I don't think it will be a problem. Certainly something to keep in mind though.
I used a pair of NOS San Remo 17" WM2 rims that I got from Cosmopolitan Motors. I think they are Ward's Riverside (Benelli?) parts. Since they're not the stock size I had to order custom length spokes from Buchanan's. The rear wheel laced up fine. The front wheel as shown is a disaster. I decided I couldn't use either of the two front hubs I had for a 160 due to various issues, so just for kicks I tried lacing the front hub from a 250 in there (shown above). Both issues I worried about proved true: the spokes were too long, and the holes in the rims aren't drilled at the right angle for such a (relatively) large hub. So I got a third 160 hub.
The problem is, hub #3 is an earlier hub so I need an external speedo drive. However, with the larger wheels I'll need a different ratio drive anyway. I'm not sure if the integrated drive is available in different ratios, so maybe it's a blessing in disguise to use the external drive. Or, as pointed out by Steve from Bevel Heaven, I could have the speedo recalibrated.
Or... I could put the tach in the headlight shell, ditch the stock speedometer and drive, and see just how inconspicously I could mount the hardware for an electronic speedometer. The speedo itself would be easily removed when the bike is parked, and the calibration issues would be solved, not to mention I wouldn't have to deal with a tach mount then. Hmm...
I ordered a 17 x 3.00 rear tire and a 17 x 2.75 front tire. The tubes, rim strips, and rear tire were shipped the next day. The front wasn't expected to ship for another month. I sure wish they had told me that BEFORE I ordered it... One month became two, and then three, and then they (JC Whitney...) cancelled the order. In the meantime I had already a different style tire in the same size, just in case. I've since replaced that tire with the one I originally wanted to use, so depending on when the picture was taken you may see the bike with different front tires..