All the "21 inch front wheel" swap/info in one place

[shotgunjoe]

Thats a stock xs650 hub.

 

[jamesgs4]

looks like it

 

[59Tebo]

Two more questions (until the next one) : if you run with dual brake rotors, can you/how do you mount the speedo to the left side of the hub, and how do you regulate the speedo for the larger diameter (fewer revolutions per mile) tire? Or is there an internal adjustment on the speedometer? And has anyone laced a front hub to a rear rim so they can have a spoked, disc brake in the rear? Don't you need a spacer for the sprocket? Okay, I'm over my limit. Shouldn't drink and type...

 

[XSLeo]

Depending on your tire size there won't be enough difference in rpms of the wheel to matter. A 100/90-19 tire is about 26.5 nches tall. A 3.00 21 tire I think is a 100 aspect ratio tire. The height of the tire from bead to tread is 100% the width of the tire. So 3+3+21= 27 inches. As I recall 1/2 difference in tire height makes 1 mph difference in the speedo reading.
Most speedos are off by about 2 mph. You are going 2 mph slower than your speedo reads. The 21 inch tire adds 1 mph. So you start 2 slow add one makes you 1 slow.
Close enough.
It doesn't matter if you have one or two disc on the wheel. The stock speedo drive clears the rotors just fine. It does on my 75 with dual disc. It works on all the dual disc European bikes. Yamaha planned for this and designed it to work.
On using a front hub on the rear, yes been done for years, Omar's sells a kit just for doing that.
Leo

 

[aldo5468]

Here's how it looks (response to #31) - 64-spoke 21" from Mike's XS