My Cateye Commuter is on my 4-stroke, yes. Like any wireless device it's susceptible to interference.
My Trek Incite 8i was used on my red bike in album. I rode it from 2006-2008 with 3 chinagirls, then used it on 2 other bikes with 2 more. The speedo is beat up, so I put it in my toolbox in 2010, but it always worked great. Probably still would with a new battery. I always ran a $5 Radio Shack clamp-on plug wire noise isolator on the 2-strokes and the speedometer would work fine as long there was no other