Originally Posted by brianpc
"One front 17" wheel, one rear 17" wheel. Those are the only NECESSARY parts."
If you buy the right wheels, this is correct. I am doing research for SM wheels also for my '13 690E, and I plan on buying wheels that will require no spacers or have fitment issues (if possible
Be sure the front wheel has the 690E brake rotor setup or you'll have to get a spacer/bracket to move the caliper.
Be sure the rear wheel has a sprocket that you can use with the stock chain - previous posts here say 40T and 42T will work if you flip the axle block adjusters around, which is about as easy as it gets. The stock enduro sprockets are 15:45, so 42T will be taller gearing but you're running a smaller wheel diameter.
The speedo will be off due to the 17" front tire being smaller than the 21", but you can switch the wheel length speedo read (690E default is 2250) to 1850 (i think?) on the computer somewhere, or you have to mess with a wire.. There's a writeup somewhere on either supermotojunkies or an SMC thread here explaining it.
You'll also want the 690SMC kickstand, the 690E stand is wayyyy too tall for the 17" wheels.
This is everything I've learned while researching for my SM wheel setup, hope this helps. Also, anybody correct me if I've missed anything or stated anything incorrectly.
Obviously you have to weigh the price to convenience aspect. Myself I went with convenience so I bought complete wheelsets including a 2nd set of cush rubbers, so all I have to do is pull off the dirt wheels and bolt on the SM wheels, I do use the same spacers for both wheel sets. It takes me about 15 minutes form start to finish.
If you want to do it on the cheap then you'll have to swap things like the sprocket carrier and brake rotors between the wheel sets so all you really need is to buy the wheels, although you will probably want to get a 40 T rear sprocket as well.
I did use the E kickstand for a while but the bike sits almost straight up. I did eventually have a buddy cut it down and re-weld the foot back on for the cost of a beer. It leans a bit more with the dirt wheels on it now but it's no big deal.